diff --git a/finnow-api/schema.sql b/finnow-api/schema.sql
index 636249d..4c0415c 100644
--- a/finnow-api/schema.sql
+++ b/finnow-api/schema.sql
@@ -31,7 +31,7 @@ CREATE TABLE account (
 
 CREATE TABLE account_credit_card_properties (
     account_id INTEGER PRIMARY KEY,
-    credit_limit TEXT,
+    credit_limit INTEGER,
     CONSTRAINT fk_account_credit_card_properties_account
         FOREIGN KEY (account_id) REFERENCES account(id)
             ON UPDATE CASCADE ON DELETE CASCADE
@@ -64,7 +64,7 @@ CREATE TABLE "transaction" (
     id INTEGER PRIMARY KEY,
     timestamp TEXT NOT NULL,
     added_at TEXT NOT NULL,
-    amount TEXT NOT NULL,
+    amount INTEGER NOT NULL,
     currency TEXT NOT NULL,
     description TEXT,
     vendor_id INTEGER,
@@ -77,4 +77,132 @@ CREATE TABLE "transaction" (
             ON UPDATE CASCADE ON DELETE SET NULL
 );
 
+CREATE TABLE transaction_attachment (
+    transaction_id INTEGER NOT NULL,
+    attachment_id INTEGER NOT NULL,
+    PRIMARY KEY (transaction_id, attachment_id),
+    CONSTRAINT fk_transaction_attachment_transaction
+        FOREIGN KEY (transaction_id) REFERENCES "transaction"(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_transaction_attachment_attachment
+        FOREIGN KEY (attachment_id) REFERENCES attachment(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
 
+CREATE TABLE transaction_tag_join (
+    transaction_id INTEGER NOT NULL,
+    tag_id INTEGER NOT NULL,
+    PRIMARY KEY (transaction_id, tag_id),
+    CONSTRAINT fk_transaction_tag_join_transaction
+        FOREIGN KEY (transaction_id) REFERENCES "transaction"(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_transaction_tag_join_tag
+        FOREIGN KEY (tag_id) REFERENCES transaction_tag(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+CREATE TABLE transaction_line_item (
+    id INTEGER PRIMARY KEY,
+    transaction_id INTEGER NOT NULL,
+    value_per_item INTEGER NOT NULL,
+    quantity INTEGER NOT NULL DEFAULT 1,
+    idx INTEGER NOT NULL DEFAULT 0,
+    description TEXT NOT NULL,
+    category_id INTEGER,
+    CONSTRAINT fk_transaction_line_item_transaction
+        FOREIGN KEY (transaction_id) REFERENCES "transaction"(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_transaction_line_item_category
+        FOREIGN KEY (category_id) REFERENCES transaction_category(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+CREATE TABLE account_journal_entry (
+    id INTEGER PRIMARY KEY,
+    timestamp TEXT NOT NULL,
+    account_id INTEGER NOT NULL,
+    transaction_id INTEGER NOT NULL,
+    amount INTEGER NOT NULL,
+    type TEXT NOT NULL,
+    currency TEXT NOT NULL,
+    CONSTRAINT fk_account_journal_entry_account
+        FOREIGN KEY (account_id) REFERENCES account(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_account_journal_entry_transaction
+        FOREIGN KEY (transaction_id) REFERENCES "transaction"(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+-- Value records
+
+CREATE TABLE account_value_record (
+    id INTEGER PRIMARY KEY,
+    timestamp TEXT NOT NULL,
+    account_id INTEGER NOT NULL,
+    type TEXT NOT NULL DEFAULT 'BALANCE',
+    balance INTEGER NOT NULL,
+    currency TEXT NOT NULL,
+    CONSTRAINT fk_balance_record_account
+        FOREIGN KEY (account_id) REFERENCES account(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+CREATE TABLE account_value_record_attachment (
+    value_record_id BIGINT NOT NULL,
+    attachment_id BIGINT NOT NULL,
+    PRIMARY KEY (value_record_id, attachment_id),
+    CONSTRAINT fk_account_value_record_attachment_value_record
+        FOREIGN KEY (value_record_id) REFERENCES account_value_record(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_account_value_record_attachment_attachment
+        FOREIGN KEY (attachment_id) REFERENCES attachment(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+-- History Entities
+
+CREATE TABLE history (
+    id INTEGER PRIMARY KEY
+);
+
+CREATE TABLE history_item (
+    id INTEGER PRIMARY KEY,
+    history_id INTEGER NOT NULL,
+    timestamp TEXT NOT NULL,
+    type TEXT NOT NULL,
+    CONSTRAINT fk_history_item_history
+        FOREIGN KEY (history_id) REFERENCES history(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+CREATE TABLE history_item_text (
+    item_id INTEGER PRIMARY KEY,
+    content TEXT NOT NULL,
+    CONSTRAINT fk_history_item_text_item
+        FOREIGN KEY (item_id) REFERENCES history_item(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+CREATE TABLE account_history (
+    account_id INTEGER NOT NULL UNIQUE,
+    history_id INTEGER NOT NULL,
+    PRIMARY KEY (account_id, history_id),
+    CONSTRAINT fk_account_history_account
+        FOREIGN KEY (account_id) REFERENCES account(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_account_history_history
+        FOREIGN KEY (history_id) REFERENCES history(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
+
+CREATE TABLE transaction_history (
+    transaction_id INTEGER NOT NULL UNIQUE,
+    history_id INTEGER NOT NULL,
+    PRIMARY KEY (transaction_id, history_id),
+    CONSTRAINT fk_history_transaction_transaction
+        FOREIGN KEY (transaction_id) REFERENCES "transaction"(id)
+            ON UPDATE CASCADE ON DELETE CASCADE,
+    CONSTRAINT fk_history_transaction_history
+        FOREIGN KEY (history_id) REFERENCES history(id)
+            ON UPDATE CASCADE ON DELETE CASCADE
+);
diff --git a/finnow-api/source/account/api.d b/finnow-api/source/account/api.d
new file mode 100644
index 0000000..2a20544
--- /dev/null
+++ b/finnow-api/source/account/api.d
@@ -0,0 +1,84 @@
+module account.api;
+
+import handy_httpd;
+import asdf;
+
+import profile.service;
+import account.model;
+import money.currency;
+
+struct AccountResponse {
+    ulong id;
+    string createdAt;
+    bool archived;
+    string type;
+    string numberSuffix;
+    string name;
+    string currency;
+    string description;
+
+    static AccountResponse of(in Account account) {
+        AccountResponse r;
+        r.id = account.id;
+        r.createdAt = account.createdAt.toISOExtString();
+        r.archived = account.archived;
+        r.type = account.type.id;
+        r.numberSuffix = account.numberSuffix;
+        r.name = account.name;
+        r.currency = account.currency.code.dup;
+        r.description = account.description;
+        return r;
+    }
+}
+
+void handleGetAccounts(ref HttpRequestContext ctx) {
+    import std.algorithm;
+    auto ds = getProfileDataSource(ctx);
+    auto accounts = ds.getAccountRepository().findAll()
+        .map!(a => AccountResponse.of(a));
+    ctx.response.writeBodyString(serializeToJson(accounts), "application/json");
+}
+
+void handleGetAccount(ref HttpRequestContext ctx) {
+    ulong accountId = ctx.request.getPathParamAs!ulong("accountId");
+    auto ds = getProfileDataSource(ctx);
+    auto account = ds.getAccountRepository().findById(accountId)
+        .orElseThrow(() => new HttpStatusException(HttpStatus.NOT_FOUND));
+    ctx.response.writeBodyString(serializeToJson(AccountResponse.of(account)), "application/json");
+}
+
+struct AccountCreationPayload {
+    string type;
+    string numberSuffix;
+    string name;
+    string currency;
+    string description;
+}
+
+void handleCreateAccount(ref HttpRequestContext ctx) {
+    auto ds = getProfileDataSource(ctx);
+    AccountCreationPayload payload;
+    try {
+        payload = deserialize!(AccountCreationPayload)(ctx.request.readBodyAsString());
+    } catch (SerdeException e) {
+        ctx.response.status = HttpStatus.BAD_REQUEST;
+        ctx.response.writeBodyString("Invalid account payload.");
+        return;
+    }
+    AccountType type = AccountType.fromId(payload.type);
+    Currency currency = Currency.ofCode(payload.currency);
+    Account account = ds.getAccountRepository().insert(
+        type,
+        payload.numberSuffix,
+        payload.name,
+        currency,
+        payload.description
+    );
+    ctx.response.writeBodyString(serializeToJson(AccountResponse.of(account)), "application/json");
+}
+
+void handleDeleteAccount(ref HttpRequestContext ctx) {
+    ulong accountId = ctx.request.getPathParamAs!ulong("accountId");
+    auto ds = getProfileDataSource(ctx);
+    ds.getAccountRepository().deleteById(accountId);
+}
diff --git a/finnow-api/source/account/data.d b/finnow-api/source/account/data.d
new file mode 100644
index 0000000..0f68af0
--- /dev/null
+++ b/finnow-api/source/account/data.d
@@ -0,0 +1,19 @@
+module account.data;
+
+import handy_httpd.components.optional;
+
+import account.model;
+import money.currency;
+import history.model;
+
+interface AccountRepository {
+    Optional!Account findById(ulong id);
+    Account insert(AccountType type, string numberSuffix, string name, Currency currency, string description);
+    void setArchived(ulong id, bool archived);
+    Account update(ulong id, in Account newData);
+    void deleteById(ulong id);
+    Account[] findAll();
+    AccountCreditCardProperties getCreditCardProperties(ulong id);
+    void setCreditCardProperties(ulong id, in AccountCreditCardProperties props);
+    History getHistory(ulong id);
+}
diff --git a/finnow-api/source/account/data_impl_sqlite.d b/finnow-api/source/account/data_impl_sqlite.d
new file mode 100644
index 0000000..e37b2b4
--- /dev/null
+++ b/finnow-api/source/account/data_impl_sqlite.d
@@ -0,0 +1,138 @@
+module account.data_impl_sqlite;
+
+import std.datetime;
+
+import d2sqlite3;
+import handy_httpd.components.optional;
+
+import account.data;
+import account.model;
+import money.currency;
+import history.model;
+import util.sqlite;
+
+class SqliteAccountRepository : AccountRepository {
+    private Database db;
+    this(Database db) {
+        this.db = db;
+    }
+
+    Optional!Account findById(ulong id) {
+        return findOne(
+            db,
+            "SELECT * FROM account WHERE id = ?",
+            &parseAccount,
+            id
+        );
+    }
+
+    Account insert(AccountType type, string numberSuffix, string name, Currency currency, string description) {
+        Statement stmt = db.prepare(q"SQL
+            INSERT INTO account
+            (created_at, type, number_suffix, name, currency, description)
+            VALUES (?, ?, ?, ?, ?, ?)
+SQL");
+        stmt.bind(1, Clock.currTime(UTC()).toISOExtString());
+        stmt.bind(2, type.id);
+        stmt.bind(3, numberSuffix);
+        stmt.bind(4, name);
+        stmt.bind(5, currency.code);
+        stmt.bind(6, description);
+        stmt.execute();
+        ulong accountId = db.lastInsertRowid();
+        return findById(accountId).orElseThrow("Couldn't find account!");
+    }
+
+    void setArchived(ulong id, bool archived) {
+        util.sqlite.update(
+            db,
+            "UPDATE account SET archived = ? WHERE id = ?",
+            archived ? 1 : 0,
+            id
+        );
+    }
+
+    Account update(ulong id, in Account newData) {
+        return newData; // TODO:
+    }
+
+    void deleteById(ulong id) {
+        doTransaction(db, () {
+            util.sqlite.update(
+                db,
+                "DELETE FROM history
+                WHERE id IN (
+                    SELECT history_id FROM account_history
+                    WHERE account_id = ?
+                )",
+                id
+            );
+            util.sqlite.update(db, "DELETE FROM account WHERE id = ?", id);
+        });
+    }
+
+    Account[] findAll() {
+        return util.sqlite.findAll(db, "SELECT * FROM account", &parseAccount);
+    }
+
+    AccountCreditCardProperties getCreditCardProperties(ulong id) {
+        Statement stmt = db.prepare("SELECT * FROM account_credit_card_properties WHERE account_id = ?");
+        stmt.bind(1, id);
+        ResultRange result = stmt.execute();
+        return parseCreditCardProperties(result.front);
+    }
+
+    void setCreditCardProperties(ulong id, in AccountCreditCardProperties props) {
+        // TODO:
+    }
+
+    History getHistory(ulong id) {
+        if (!exists(db, "SELECT id FROM account WHERE id = ?", id)) {
+            throw new Exception("Account doesn't exist.");
+        }
+        Optional!History history = findOne(
+            db,
+            q"SQL
+        SELECT * FROM history
+        LEFT JOIN account_history ah ON ah.history_id = history.id
+        WHERE ah.account_id = ?
+SQL",
+            r => History(r.peek!ulong(0)),
+            id
+        );
+        if (!history.empty) {
+            return history.value;
+        }
+        // No history exists yet, so add it.
+        ulong historyId = doTransaction(db, () {
+            util.sqlite.update(db, "INSERT INTO history DEFAULT VALUES");
+            ulong historyId = db.lastInsertRowid();
+            util.sqlite.update(db, "INSERT INTO account_history (account_id, history_id) VALUES (?, ?)", id, historyId);
+            return historyId;
+        });
+        return History(historyId);
+    }
+
+    static Account parseAccount(Row row) {
+        return Account(
+            row.peek!ulong(0),
+            SysTime.fromISOExtString(row.peek!string(1)),
+            row.peek!bool(2),
+            AccountType.fromId(row.peek!string(3)),
+            row.peek!string(4),
+            row.peek!string(5),
+            Currency.ofCode(row.peek!string(6)),
+            row.peek!string(7)
+        );
+    }
+
+    static AccountCreditCardProperties parseCreditCardProperties(Row row) {
+        import std.typecons : Nullable;
+        ulong accountId = row.peek!ulong(0);
+        Nullable!ulong creditLimit = row.peek!ulong(1);
+        return AccountCreditCardProperties(
+            accountId,
+            creditLimit.isNull ? -1 : creditLimit.get()
+        );
+    }
+}
diff --git a/finnow-api/source/account/model.d b/finnow-api/source/account/model.d
new file mode 100644
index 0000000..cadcc6b
--- /dev/null
+++ b/finnow-api/source/account/model.d
@@ -0,0 +1,42 @@
+module account.model;
+
+import std.datetime;
+
+import money.currency;
+
+struct AccountType {
+    const string id;
+    const string name;
+    const bool debitsPositive;
+
+    import std.traits : EnumMembers;
+    static AccountType fromId(string id) {
+        static foreach (t; EnumMembers!AccountTypes) {
+            if (id == t.id) return t;
+        }
+        throw new Exception("Invalid account type id " ~ id);
+    }
+}
+
+enum AccountTypes : AccountType {
+    CHECKING = AccountType("CHECKING", "Checking", true),
+    SAVINGS = AccountType("SAVINGS", "Savings", true),
+    CREDIT_CARD = AccountType("CREDIT_CARD", "Credit Card", false),
+    BROKERAGE = AccountType("BROKERAGE", "Brokerage", true)
+}
+
+struct Account {
+    ulong id;
+    SysTime createdAt;
+    bool archived;
+    AccountType type;
+    string numberSuffix;
+    string name;
+    Currency currency;
+    string description;
+}
+
+struct AccountCreditCardProperties {
+    ulong account_id;
+    long creditLimit;
+}
diff --git a/finnow-api/source/api_mapping.d b/finnow-api/source/api_mapping.d
new file mode 100644
index 0000000..71703ef
--- /dev/null
+++ b/finnow-api/source/api_mapping.d
@@ -0,0 +1,58 @@
+module api_mapping;
+
+import handy_httpd;
+import handy_httpd.handlers.path_handler;
+import handy_httpd.handlers.filtered_handler;
+
+/**
+ * Defines the Finnow API mapping with a main PathHandler.
+ * Returns: The handler to plug into an HttpServer.
+ */
+PathHandler mapApiHandlers() {
+	/// The base path to all API endpoints.
+    const API_PATH = "/api";
+	PathHandler h = new PathHandler();
+
+	// Generic, public endpoints:
+	h.addMapping(Method.GET, API_PATH ~ "/status", &getStatus);
+	h.addMapping(Method.OPTIONS, API_PATH ~ "/**", &getOptions);
+	
+	// Auth endpoints:
+	import auth.api;
+	h.addMapping(Method.POST, API_PATH ~ "/login", &postLogin);
+	h.addMapping(Method.POST, API_PATH ~ "/register", &postRegister);
+
+	// Authenticated endpoints:
+	PathHandler a = new PathHandler();
+	a.addMapping(Method.GET, API_PATH ~ "/me", &getMyUser);
+	
+    import profile.api;
+	a.addMapping(Method.GET, API_PATH ~ "/profiles", &handleGetProfiles);
+	a.addMapping(Method.POST, API_PATH ~ "/profiles", &handleCreateNewProfile);
+	/// URL path to a specific profile, with the :profile path parameter.
+	const PROFILE_PATH = API_PATH ~ "/profiles/:profile";
+	a.addMapping(Method.DELETE, PROFILE_PATH, &handleDeleteProfile);
+	a.addMapping(Method.GET, PROFILE_PATH ~ "/properties", &handleGetProperties);
+
+    import account.api;
+    a.addMapping(Method.GET, PROFILE_PATH ~ "/accounts", &handleGetAccounts);
+	a.addMapping(Method.POST, PROFILE_PATH ~ "/accounts", &handleCreateAccount);
+	a.addMapping(Method.GET, PROFILE_PATH ~ "/accounts/:accountId:ulong", &handleGetAccount);
+	a.addMapping(Method.DELETE, PROFILE_PATH ~ "/accounts/:accountId:ulong", &handleDeleteAccount);
+
+    // Protect all authenticated paths with a token filter.
+	import auth.service : TokenAuthenticationFilter, SECRET;
+	HttpRequestFilter tokenAuthenticationFilter = new TokenAuthenticationFilter(SECRET);
+	h.addMapping(API_PATH ~ "/**", new FilteredRequestHandler(
+		a,
+		[tokenAuthenticationFilter]
+	));
+
+	return h;
+}
+
+private void getStatus(ref HttpRequestContext ctx) {
+    ctx.response.writeBodyString("online");
+}
+
+private void getOptions(ref HttpRequestContext ctx) {}
diff --git a/finnow-api/source/app.d b/finnow-api/source/app.d
index 0c59fa1..3aaff62 100644
--- a/finnow-api/source/app.d
+++ b/finnow-api/source/app.d
@@ -1,50 +1,10 @@
-import slf4d;
 import handy_httpd;
-import handy_httpd.handlers.path_handler;
-import handy_httpd.handlers.filtered_handler;
+import api_mapping;
 
 void main() {
 	ServerConfig cfg;
 	cfg.workerPoolSize = 5;
 	cfg.port = 8080;
-	HttpServer server = new HttpServer(buildHandlers(), cfg);
+	HttpServer server = new HttpServer(mapApiHandlers(), cfg);
 	server.start();
 }
-
-PathHandler buildHandlers() {
-	import profile;
-	
-	const API_PATH = "/api";
-	PathHandler pathHandler = new PathHandler();
-
-	// Generic, public endpoints:
-	pathHandler.addMapping(Method.GET, API_PATH ~ "/status", (ref ctx) {
-		ctx.response.writeBodyString("online");
-	});
-	pathHandler.addMapping(Method.OPTIONS, API_PATH ~ "/**", (ref ctx) {});
-	
-	// Auth Entrypoints:
-	import auth.api;
-	import auth.service;
-	pathHandler.addMapping(Method.POST, API_PATH ~ "/login", &postLogin);
-	pathHandler.addMapping(Method.POST, API_PATH ~ "/register", &postRegister);
-
-	// Authenticated endpoints:
-	PathHandler a = new PathHandler();
-	a.addMapping(Method.GET, API_PATH ~ "/me", &getMyUser);
-	a.addMapping(Method.GET, API_PATH ~ "/profiles", &handleGetProfiles);
-	a.addMapping(Method.POST, API_PATH ~ "/profiles", &handleCreateNewProfile);
-	a.addMapping(Method.DELETE, API_PATH ~ "/profiles/:name", &handleDeleteProfile);
-	a.addMapping(Method.GET, API_PATH ~ "/profiles/:profile/properties", &handleGetProperties);
-	a.addMapping(Method.GET, API_PATH ~ "/profiles/:profile/accounts", (ref ctx) {
-		ctx.response.writeBodyString("your accounts!");
-	});
-
-	HttpRequestFilter tokenAuthenticationFilter = new TokenAuthenticationFilter(SECRET);
-	pathHandler.addMapping(API_PATH ~ "/**", new FilteredRequestHandler(
-		a,
-		[tokenAuthenticationFilter]
-	));
-
-	return pathHandler;
-}
diff --git a/finnow-api/source/model/base.d b/finnow-api/source/attachment/model.d
similarity index 65%
rename from finnow-api/source/model/base.d
rename to finnow-api/source/attachment/model.d
index b0f033e..97c5461 100644
--- a/finnow-api/source/model/base.d
+++ b/finnow-api/source/attachment/model.d
@@ -1,12 +1,7 @@
-module model.base;
+module attachment.model;
 
 import std.datetime;
 
-struct ProfileProperty {
-    string property;
-    string value;
-}
-
 struct Attachment {
     ulong id;
     SysTime uploadedAt;
diff --git a/finnow-api/source/auth/api.d b/finnow-api/source/auth/api.d
index 0806db1..f5f5d8b 100644
--- a/finnow-api/source/auth/api.d
+++ b/finnow-api/source/auth/api.d
@@ -4,16 +4,17 @@ module auth.api;
 import handy_httpd;
 import handy_httpd.components.optional;
 import slf4d;
+import asdf;
 
 import auth.model;
-import auth.dao;
-import auth.dto;
+import auth.data;
 import auth.service;
+import auth.data_impl_fs;
 
 void postLogin(ref HttpRequestContext ctx) {
     LoginCredentials loginCredentials;
     try {
-        loginCredentials = LoginCredentials.parse(ctx.request.readBodyAsJson());
+        loginCredentials = deserialize!(LoginCredentials)(ctx.request.readBodyAsString());
     } catch (Exception e) {
         ctx.response.status = HttpStatus.BAD_REQUEST;
     }
@@ -34,13 +35,14 @@ void postLogin(ref HttpRequestContext ctx) {
     }
     string token = generateAccessToken(optionalUser.value);
     ctx.response.status = HttpStatus.OK;
-    ctx.response.writeBodyString(TokenResponse(token).toJson(), "application/json");
+    TokenResponse resp = TokenResponse(token);
+    ctx.response.writeBodyString(serializeToJson(resp), "application/json");
 }
 
 void postRegister(ref HttpRequestContext ctx) {
     RegistrationData registrationData;
     try {
-        registrationData = RegistrationData.parse(ctx.request.readBodyAsJson());
+        registrationData = deserialize!(RegistrationData)(ctx.request.readBodyAsString());
     } catch (Exception e) {
         ctx.response.status = HttpStatus.BAD_REQUEST;
         return;
diff --git a/finnow-api/source/auth/data.d b/finnow-api/source/auth/data.d
new file mode 100644
index 0000000..086b8bd
--- /dev/null
+++ b/finnow-api/source/auth/data.d
@@ -0,0 +1,26 @@
+module auth.data;
+
+import handy_httpd.components.optional;
+import auth.model;
+
+/// The credentials provided by a user to login.
+struct LoginCredentials {
+    string username;
+    string password;
+}
+
+/// A token response sent to the user if they've been authenticated.
+struct TokenResponse {
+    string token;
+}
+
+struct RegistrationData {
+    string username;
+    string password;
+}
+
+interface UserRepository {
+    Optional!User findByUsername(string username);
+    User createUser(string username, string passwordHash);
+    void deleteByUsername(string username);
+}
diff --git a/finnow-api/source/auth/dao.d b/finnow-api/source/auth/data_impl_fs.d
similarity index 90%
rename from finnow-api/source/auth/dao.d
rename to finnow-api/source/auth/data_impl_fs.d
index c10e224..f63cb53 100644
--- a/finnow-api/source/auth/dao.d
+++ b/finnow-api/source/auth/data_impl_fs.d
@@ -1,13 +1,9 @@
-module auth.dao;
+module auth.data_impl_fs;
 
 import handy_httpd.components.optional;
-import auth.model;
 
-interface UserRepository {
-    Optional!User findByUsername(string username);
-    User createUser(string username, string passwordHash);
-    void deleteByUsername(string username);
-}
+import auth.data;
+import auth.model;
 
 /**
  * User implementation that stores each user's data in a separate directory.
@@ -63,4 +59,4 @@ class FileSystemUserRepository : UserRepository {
     private string getUserDataFile(string username) {
         return buildPath(this.usersDir, username, "user-data.json");
     }
-}
+}
\ No newline at end of file
diff --git a/finnow-api/source/auth/dto.d b/finnow-api/source/auth/dto.d
deleted file mode 100644
index 798fbf2..0000000
--- a/finnow-api/source/auth/dto.d
+++ /dev/null
@@ -1,46 +0,0 @@
-/// Defines data-transfer objects for the API's authentication mechanisms.
-module auth.dto;
-
-import handy_httpd;
-import std.json;
-
-struct LoginCredentials {
-    string username;
-    string password;
-
-    static LoginCredentials parse(JSONValue obj) {
-        if (
-            obj.type != JSONType.OBJECT ||
-            "username" !in obj.object ||
-            "password" !in obj.object ||
-            obj.object["username"].type != JSONType.STRING ||
-            obj.object["password"].type != JSONType.STRING
-        ) {
-            throw new HttpStatusException(HttpStatus.BAD_REQUEST, "Malformed login credentials.");
-        }
-        return LoginCredentials(
-            obj.object["username"].str,
-            obj.object["password"].str
-        );
-    }
-}
-
-struct TokenResponse {
-    string token;
-
-    string toJson() {
-        JSONValue obj = JSONValue.emptyObject;
-        obj.object["token"] = JSONValue(token);
-        return obj.toString();
-    }
-}
-
-struct RegistrationData {
-    string username;
-    string password;
-
-    static RegistrationData parse(JSONValue obj) {
-        LoginCredentials lc = LoginCredentials.parse(obj);
-        return RegistrationData(lc.username, lc.password);
-    }
-}
\ No newline at end of file
diff --git a/finnow-api/source/auth/service.d b/finnow-api/source/auth/service.d
index c26ab48..a0a455f 100644
--- a/finnow-api/source/auth/service.d
+++ b/finnow-api/source/auth/service.d
@@ -2,11 +2,12 @@ module auth.service;
 
 import handy_httpd;
 import handy_httpd.components.optional;
+import handy_httpd.handlers.filtered_handler;
 import slf4d;
 
 import auth.model;
-import auth.dao;
-import handy_httpd.handlers.filtered_handler;
+import auth.data;
+import auth.data_impl_fs;
 
 const SECRET = "temporary-insecure-secret"; // TODO: Load secret from application config!
 
@@ -66,7 +67,7 @@ class AuthContext {
  *   ctx = The request context to get.
  * Returns: The auth context that has been set.
  */
-AuthContext getAuthContext(ref HttpRequestContext ctx) {
+AuthContext getAuthContext(in HttpRequestContext ctx) {
     return cast(AuthContext) ctx.metadata[TokenAuthenticationFilter.AUTH_METADATA_KEY];
 }
 
diff --git a/finnow-api/source/data/account.d b/finnow-api/source/data/account.d
deleted file mode 100644
index 0ee7170..0000000
--- a/finnow-api/source/data/account.d
+++ /dev/null
@@ -1,2 +0,0 @@
-module data.account;
-
diff --git a/finnow-api/source/data/base.d b/finnow-api/source/data/base.d
deleted file mode 100644
index 248adfd..0000000
--- a/finnow-api/source/data/base.d
+++ /dev/null
@@ -1,15 +0,0 @@
-module data.base;
-
-import model;
-import handy_httpd.components.optional;
-
-interface DataSource {
-    PropertiesRepository getPropertiesRepository();
-}
-
-interface PropertiesRepository {
-    Optional!string findProperty(string propertyName);
-    void setProperty(string name, string value);
-    void deleteProperty(string name);
-    ProfileProperty[] findAll();
-}
diff --git a/finnow-api/source/data/package.d b/finnow-api/source/data/package.d
deleted file mode 100644
index 597bcbd..0000000
--- a/finnow-api/source/data/package.d
+++ /dev/null
@@ -1,6 +0,0 @@
-module data;
-
-public import data.base;
-
-// Utility imports for items commonly used alongside data.
-public import handy_httpd.components.optional;
diff --git a/finnow-api/source/data/sqlite.d b/finnow-api/source/data/sqlite.d
deleted file mode 100644
index 92e56b7..0000000
--- a/finnow-api/source/data/sqlite.d
+++ /dev/null
@@ -1,82 +0,0 @@
-module data.sqlite;
-
-import d2sqlite3;
-import slf4d;
-import data.base;
-import model;
-
-class SqliteDataSource : DataSource {
-    const SCHEMA = import("schema.sql");
-
-    private const string dbPath;
-    private Database db;
-
-    this(string path) {
-        this.dbPath = path;
-        import std.file : exists;
-        bool needsInit = !exists(path);
-        this.db = Database(path);
-        if (needsInit) {
-            infoF!"Initializing database: %s"(dbPath);
-            db.run(SCHEMA);
-        }
-    }
-
-    PropertiesRepository getPropertiesRepository() {
-        return new SqlitePropertiesRepository(db);
-    }
-}
-
-class SqliteRepository {
-    private Database db;
-    this(Database db) {
-        this.db = db;
-    }
-}
-
-class SqlitePropertiesRepository : SqliteRepository, PropertiesRepository {
-    this(Database db) {
-        super(db);
-    }
-
-    Optional!string findProperty(string propertyName) {
-        Statement stmt = this.db.prepare("SELECT value FROM profile_property WHERE property = ?");
-        stmt.bind(1, propertyName);
-        ResultRange result = stmt.execute();
-        if (result.empty) return Optional!string.empty;
-        return Optional!string.of(result.front.peek!string(0));
-    }
-
-    void setProperty(string name, string value) {
-        if (findProperty(name).isNull) {
-            Statement stmt = this.db.prepare("INSERT INTO profile_property (property, value) VALUES (?, ?)");
-            stmt.bind(1, name);
-            stmt.bind(2, value);
-            stmt.execute();
-        } else {
-            Statement stmt = this.db.prepare("UPDATE profile_property SET value = ? WHERE property = ?");
-            stmt.bind(1, value);
-            stmt.bind(2, name);
-            stmt.execute();
-        }
-    }
-
-    void deleteProperty(string name) {
-        Statement stmt = this.db.prepare("DELETE FROM profile_property WHERE property = ?");
-        stmt.bind(1, name);
-        stmt.execute();
-    }
-
-    ProfileProperty[] findAll() {
-        Statement stmt = this.db.prepare("SELECT * FROM profile_property ORDER BY property ASC");
-        ResultRange result = stmt.execute();
-        ProfileProperty[] props;
-        foreach (Row row; result) {
-            ProfileProperty prop;
-            prop.property = row.peek!string("property");
-            prop.value = row.peek!string("value");
-            props ~= prop;
-        }
-        return props;
-    }
-}
diff --git a/finnow-api/source/history/data.d b/finnow-api/source/history/data.d
new file mode 100644
index 0000000..94a4c44
--- /dev/null
+++ b/finnow-api/source/history/data.d
@@ -0,0 +1,14 @@
+module history.data;
+
+import std.datetime;
+
+import handy_httpd.components.optional;
+
+import history.model;
+
+interface HistoryRepository {
+    Optional!History findById(ulong id);
+    HistoryItem[] findItemsBefore(ulong historyId, SysTime timestamp, uint limit);
+    HistoryItemText getTextItem(ulong itemId);
+    void deleteById(ulong id);
+}
\ No newline at end of file
diff --git a/finnow-api/source/history/data_impl_sqlite.d b/finnow-api/source/history/data_impl_sqlite.d
new file mode 100644
index 0000000..b4f1ffd
--- /dev/null
+++ b/finnow-api/source/history/data_impl_sqlite.d
@@ -0,0 +1,75 @@
+module history.data_impl_sqlite;
+
+import std.datetime;
+
+import handy_httpd.components.optional;
+import d2sqlite3;
+
+import history.data;
+import history.model;
+
+class SqliteHistoryRepository : HistoryRepository {
+    private Database db;
+    this(Database db) {
+        this.db = db;
+    }
+
+    Optional!History findById(ulong id) {
+        Statement stmt = db.prepare("SELECT * FROM history WHERE id = ?");
+        stmt.bind(1, id);
+        ResultRange result = stmt.execute();
+        if (result.empty) return Optional!History.empty;
+        return Optional!History.of(parseHistory(result.front));
+    }
+
+    HistoryItem[] findItemsBefore(ulong historyId, SysTime timestamp, uint limit) {
+        import std.conv;
+        import std.algorithm;
+        import std.array;
+        const query = q"SQL
+            SELECT * FROM history_item
+            WHERE history_id = ? AND timestamp <= ?
+            ORDER BY timestamp DESC
+            LIMIT
+SQL";
+        Statement stmt = db.prepare(query ~ " " ~ to!string(limit));
+        stmt.bind(1, historyId);
+        stmt.bind(2, timestamp.toISOExtString());
+        ResultRange result = stmt.execute();
+        return result.map!(r => parseItem(r)).array;
+    }
+
+    HistoryItemText getTextItem(ulong itemId) {
+        Statement stmt = db.prepare("SELECT * FROM history_item_text WHERE item_id = ?");
+        stmt.bind(1, itemId);
+        ResultRange result = stmt.execute();
+        if (result.empty) throw new Exception("No history item exists.");
+        return parseTextItem(result.front);
+    }
+
+    void deleteById(ulong id) {
+        Statement stmt = db.prepare("DELETE FROM history WHERE id = ?");
+        stmt.bind(1, id);
+        stmt.execute();
+    }
+
+    static History parseHistory(Row row) {
+        return History(row.peek!ulong(0));
+    }
+
+    static HistoryItem parseItem(Row row) {
+        HistoryItem item;
+        item.id = row.peek!ulong(0);
+        item.historyId = row.peek!ulong(1);
+        item.timestamp = SysTime.fromISOExtString(row.peek!string(2));
+        item.type = getHistoryItemType(row.peek!string(3));
+        return item;
+    }
+
+    static HistoryItemText parseTextItem(Row row) {
+        HistoryItemText item;
+        item.itemId = row.peek!ulong(0);
+        item.content = row.peek!string(1);
+        return item;
+    }
+}
\ No newline at end of file
diff --git a/finnow-api/source/history/model.d b/finnow-api/source/history/model.d
new file mode 100644
index 0000000..5ba850e
--- /dev/null
+++ b/finnow-api/source/history/model.d
@@ -0,0 +1,31 @@
+module history.model;
+
+import std.datetime.systime;
+
+struct History {
+    ulong id;
+}
+
+enum HistoryItemType : string {
+    TEXT = "TEXT"
+}
+
+HistoryItemType getHistoryItemType(string text) {
+    import std.traits;
+    static foreach (t; EnumMembers!HistoryItemType) {
+        if (text == t) return t;
+    }
+    throw new Exception("Unknown history item type: " ~ text);
+}
+
+struct HistoryItem {
+    ulong id;
+    ulong historyId;
+    SysTime timestamp;
+    HistoryItemType type;
+}
+
+struct HistoryItemText {
+    ulong itemId;
+    string content;
+}
diff --git a/finnow-api/source/model/account.d b/finnow-api/source/model/account.d
deleted file mode 100644
index 3b6fd8e..0000000
--- a/finnow-api/source/model/account.d
+++ /dev/null
@@ -1,20 +0,0 @@
-module model.account;
-
-import model.base;
-import std.datetime;
-
-struct Account {
-    ulong id;
-    SysTime createdAt;
-    bool archived;
-    string type;
-    string numberSuffix;
-    string name;
-    string currency;
-    string description;
-}
-
-struct AccountCreditCardProperties {
-    ulong account_id;
-    string creditLimit;
-}
diff --git a/finnow-api/source/model/package.d b/finnow-api/source/model/package.d
deleted file mode 100644
index fbc32a3..0000000
--- a/finnow-api/source/model/package.d
+++ /dev/null
@@ -1,8 +0,0 @@
-module model;
-
-public import model.base;
-public import model.account;
-public import model.transaction;
-
-// Additional utility imports used often alongside models.
-public import handy_httpd.components.optional;
\ No newline at end of file
diff --git a/finnow-api/source/model/currency.d b/finnow-api/source/money/currency.d
similarity index 97%
rename from finnow-api/source/model/currency.d
rename to finnow-api/source/money/currency.d
index 8d9ba75..57ad708 100644
--- a/finnow-api/source/model/currency.d
+++ b/finnow-api/source/money/currency.d
@@ -1,4 +1,4 @@
-module model.currency;
+module money.currency;
 
 struct Currency {
     const char[3] code;
diff --git a/finnow-api/source/profile.d b/finnow-api/source/profile.d
deleted file mode 100644
index a763e2b..0000000
--- a/finnow-api/source/profile.d
+++ /dev/null
@@ -1,214 +0,0 @@
-/**
- * This module contains everything related to a user's Profiles, including
- * data repositories, API endpoints, models, and logic.
- */
-module profile;
-
-import handy_httpd;
-import handy_httpd.components.optional;
-import auth.model : User;
-import auth.service : AuthContext, getAuthContext;
-import data;
-import model;
-
-import std.json;
-import asdf;
-
-const DEFAULT_USERS_DIR = "users";
-
-/**
- * A profile is a complete set of Finnow financial data, all stored in one
- * single database file. The profile's name is used to lookup the database
- * partition for its data. A user may own multiple profiles.
- */
-class Profile {
-    string name;
-
-    this(string name) {
-        this.name = name;
-    }
-
-    override int opCmp(Object other) const {
-        if (Profile p = cast(Profile) other) {
-            return this.name < p.name;
-        }
-        return 1;
-    }
-}
-
-/**
- * Validates a profile name.
- * Params:
- *   name = The name to check.
- * Returns: True if the profile name is valid.
- */
-bool validateProfileName(string name) {
-    import std.regex;
-    import std.uni : toLower;
-    if (name is null || name.length < 3) return false;
-    auto r = ctRegex!(`^[a-zA-Z]+[a-zA-Z0-9_]+$`);
-    return !matchFirst(name, r).empty;
-}
-
-interface ProfileRepository {
-    Optional!Profile findByName(string name);
-    Profile createProfile(string name);
-    Profile[] findAll();
-    void deleteByName(string name);
-    DataSource getDataSource(in Profile profile);
-}
-
-class FileSystemProfileRepository : ProfileRepository {
-    import std.path;
-    import std.file;
-    import data;
-    import data.sqlite;
-
-    private const string usersDir;
-    private const string username;
-
-    this(string usersDir, string username) {
-        this.usersDir = usersDir;
-        this.username = username;
-    }
-
-    this(string username) {
-        this(DEFAULT_USERS_DIR, username);
-    }
-
-    Optional!Profile findByName(string name) {
-        string path = getProfilePath(name);
-        if (!exists(path)) return Optional!Profile.empty;
-        return Optional!Profile.of(new Profile(name));
-    }
-
-    Profile createProfile(string name) {
-        string path = getProfilePath(name);
-        if (exists(path)) throw new HttpStatusException(HttpStatus.BAD_REQUEST, "Profile already exists.");
-        if (!exists(getProfilesDir())) mkdir(getProfilesDir());
-        DataSource ds = new SqliteDataSource(path);
-        import std.datetime;
-        auto propsRepo = ds.getPropertiesRepository();
-        propsRepo.setProperty("name", name);
-        propsRepo.setProperty("createdAt", Clock.currTime(UTC()).toISOExtString());
-        propsRepo.setProperty("user", username);
-        return new Profile(name);
-    }
-
-    Profile[] findAll() {
-        string profilesDir = getProfilesDir();
-        if (!exists(profilesDir)) return [];
-        Profile[] profiles;
-        foreach (DirEntry entry; dirEntries(profilesDir, SpanMode.shallow, false)) {
-            import std.string : endsWith;
-            const suffix = ".sqlite";
-            if (endsWith(entry.name, suffix)) {
-                string profileName = baseName(entry.name, suffix);
-                profiles ~= new Profile(profileName);
-            }
-        }
-        import std.algorithm.sorting : sort;
-        sort(profiles);
-        return profiles;
-    }
-
-    void deleteByName(string name) {
-        string path = getProfilePath(name);
-        if (exists(path)) {
-            std.file.remove(path);
-        }
-    }
-
-    DataSource getDataSource(in Profile profile) {
-        return new SqliteDataSource(getProfilePath(profile.name));
-    }
-
-    private string getProfilesDir() {
-        return buildPath(this.usersDir, username, "profiles");
-    }
-
-    private string getProfilePath(string name) {
-        return buildPath(this.usersDir, username, "profiles", name ~ ".sqlite");
-    }
-}
-
-// API Endpoints Below Here!
-
-void handleCreateNewProfile(ref HttpRequestContext ctx) {
-    JSONValue obj = ctx.request.readBodyAsJson();
-    string name = obj.object["name"].str;
-    if (!validateProfileName(name)) {
-        ctx.response.status = HttpStatus.BAD_REQUEST;
-        ctx.response.writeBodyString("Invalid profile name.");
-        return;
-    }
-    AuthContext auth = getAuthContext(ctx);
-    ProfileRepository profileRepo = new FileSystemProfileRepository(auth.user.username);
-    profileRepo.createProfile(name);
-}
-
-void handleGetProfiles(ref HttpRequestContext ctx) {
-    AuthContext auth = getAuthContext(ctx);
-    ProfileRepository profileRepo = new FileSystemProfileRepository(auth.user.username);
-    Profile[] profiles = profileRepo.findAll();
-    ctx.response.writeBodyString(serializeToJson(profiles), "application/json");
-}
-
-void handleDeleteProfile(ref HttpRequestContext ctx) {
-    string name = ctx.request.getPathParamAs!string("name");
-    if (!validateProfileName(name)) {
-        ctx.response.status = HttpStatus.BAD_REQUEST;
-        ctx.response.writeBodyString("Invalid profile name.");
-        return;
-    }
-    AuthContext auth = getAuthContext(ctx);
-    ProfileRepository profileRepo = new FileSystemProfileRepository(auth.user.username);
-    profileRepo.deleteByName(name);
-}
-
-void handleGetProperties(ref HttpRequestContext ctx) {
-    ProfileContext profileCtx = getProfileContextOrThrow(ctx);
-    ProfileRepository profileRepo = new FileSystemProfileRepository(profileCtx.user.username);
-    DataSource ds = profileRepo.getDataSource(profileCtx.profile);
-    auto propsRepo = ds.getPropertiesRepository();
-    ProfileProperty[] props = propsRepo.findAll();
-    ctx.response.writeBodyString(serializeToJson(props), "application/json");
-}
-
-/// Contextual information that's available when handling requests under a profile.
-struct ProfileContext {
-    const Profile profile;
-    const User user;
-}
-
-/**
- * Tries to get a profile context from a request context. This will attempt to
- * extract a "profile" path parameter and the authenticated user, and combine
- * them into the ProfileContext.
- * Params:
- *   ctx = The request context to read.
- * Returns: An optional profile context.
- */
-Optional!ProfileContext getProfileContext(ref HttpRequestContext ctx) {
-    import auth.service : AuthContext, getAuthContext;
-    if ("profile" !in ctx.request.pathParams) return Optional!ProfileContext.empty;
-    string profileName = ctx.request.pathParams["profile"];
-    if (!validateProfileName(profileName)) return Optional!ProfileContext.empty;
-    AuthContext authCtx = getAuthContext(ctx);
-    if (authCtx is null) return Optional!ProfileContext.empty;
-    User user = authCtx.user;
-    ProfileRepository repo = new FileSystemProfileRepository("users", user.username);
-    return repo.findByName(profileName)
-        .mapIfPresent!(p => ProfileContext(p, user));
-}
-
-/**
- * Similar to `getProfileContext`, but throws an HttpStatusException with a
- * 404 NOT FOUND status if no profile context could be obtained.
- * Params:
- *   ctx = The request context to read.
- * Returns: The profile context that was obtained.
- */
-ProfileContext getProfileContextOrThrow(ref HttpRequestContext ctx) {
-    return getProfileContext(ctx).orElseThrow(() => new HttpStatusException(HttpStatus.NOT_FOUND));
-}
diff --git a/finnow-api/source/profile/api.d b/finnow-api/source/profile/api.d
new file mode 100644
index 0000000..27c9001
--- /dev/null
+++ b/finnow-api/source/profile/api.d
@@ -0,0 +1,54 @@
+module profile.api;
+
+import std.json;
+
+import handy_httpd;
+import asdf;
+
+import profile.model;
+import profile.service;
+import profile.data;
+import profile.data_impl_sqlite;
+import auth.model;
+import auth.service;
+
+void handleCreateNewProfile(ref HttpRequestContext ctx) {
+    JSONValue obj = ctx.request.readBodyAsJson();
+    string name = obj.object["name"].str;
+    if (!validateProfileName(name)) {
+        ctx.response.status = HttpStatus.BAD_REQUEST;
+        ctx.response.writeBodyString("Invalid profile name.");
+        return;
+    }
+    AuthContext auth = getAuthContext(ctx);
+    ProfileRepository profileRepo = new FileSystemProfileRepository(auth.user.username);
+    profileRepo.createProfile(name);
+}
+
+void handleGetProfiles(ref HttpRequestContext ctx) {
+    AuthContext auth = getAuthContext(ctx);
+    ProfileRepository profileRepo = new FileSystemProfileRepository(auth.user.username);
+    Profile[] profiles = profileRepo.findAll();
+    ctx.response.writeBodyString(serializeToJson(profiles), "application/json");
+}
+
+void handleDeleteProfile(ref HttpRequestContext ctx) {
+    string name = ctx.request.getPathParamAs!string("name");
+    if (!validateProfileName(name)) {
+        ctx.response.status = HttpStatus.BAD_REQUEST;
+        ctx.response.writeBodyString("Invalid profile name.");
+        return;
+    }
+    AuthContext auth = getAuthContext(ctx);
+    ProfileRepository profileRepo = new FileSystemProfileRepository(auth.user.username);
+    profileRepo.deleteByName(name);
+}
+
+void handleGetProperties(ref HttpRequestContext ctx) {
+    ProfileContext profileCtx = getProfileContextOrThrow(ctx);
+    ProfileRepository profileRepo = new FileSystemProfileRepository(profileCtx.user.username);
+    ProfileDataSource ds = profileRepo.getDataSource(profileCtx.profile);
+    auto propsRepo = ds.getPropertiesRepository();
+    ProfileProperty[] props = propsRepo.findAll();
+    ctx.response.writeBodyString(serializeToJson(props), "application/json");
+}
\ No newline at end of file
diff --git a/finnow-api/source/profile/data.d b/finnow-api/source/profile/data.d
new file mode 100644
index 0000000..7e6ef1f
--- /dev/null
+++ b/finnow-api/source/profile/data.d
@@ -0,0 +1,30 @@
+module profile.data;
+
+import handy_httpd.components.optional;
+import profile.model;
+
+interface ProfileRepository {
+    Optional!Profile findByName(string name);
+    Profile createProfile(string name);
+    Profile[] findAll();
+    void deleteByName(string name);
+    ProfileDataSource getDataSource(in Profile profile);
+}
+
+interface PropertiesRepository {
+    Optional!string findProperty(string propertyName);
+    void setProperty(string name, string value);
+    void deleteProperty(string name);
+    ProfileProperty[] findAll();
+}
+
+/**
+ * A data source for all data contained within a profile. This serves as the
+ * gateway for all data access operations for a profile.
+ */
+interface ProfileDataSource {
+    import account.data : AccountRepository;
+
+    PropertiesRepository getPropertiesRepository();
+    AccountRepository getAccountRepository();
+}
diff --git a/finnow-api/source/profile/data_impl_sqlite.d b/finnow-api/source/profile/data_impl_sqlite.d
new file mode 100644
index 0000000..7a4250a
--- /dev/null
+++ b/finnow-api/source/profile/data_impl_sqlite.d
@@ -0,0 +1,171 @@
+module profile.data_impl_sqlite;
+
+import slf4d;
+import handy_httpd.components.optional;
+import handy_httpd.components.handler : HttpStatusException;
+import handy_httpd.components.response : HttpStatus;
+import d2sqlite3;
+
+import profile.data;
+import profile.model;
+import util.sqlite;
+
+const DEFAULT_USERS_DIR = "users";
+
+class FileSystemProfileRepository : ProfileRepository {
+    import std.path;
+    import std.file;
+
+    private const string usersDir;
+    private const string username;
+
+    this(string usersDir, string username) {
+        this.usersDir = usersDir;
+        this.username = username;
+    }
+
+    this(string username) {
+        this(DEFAULT_USERS_DIR, username);
+    }
+
+    Optional!Profile findByName(string name) {
+        string path = getProfilePath(name);
+        if (!exists(path)) return Optional!Profile.empty;
+        return Optional!Profile.of(new Profile(name));
+    }
+
+    Profile createProfile(string name) {
+        string path = getProfilePath(name);
+        if (exists(path)) throw new HttpStatusException(HttpStatus.BAD_REQUEST, "Profile already exists.");
+        if (!exists(getProfilesDir())) mkdir(getProfilesDir());
+        ProfileDataSource ds = new SqliteProfileDataSource(path);
+        import std.datetime;
+        auto propsRepo = ds.getPropertiesRepository();
+        propsRepo.setProperty("name", name);
+        propsRepo.setProperty("createdAt", Clock.currTime(UTC()).toISOExtString());
+        propsRepo.setProperty("user", username);
+        return new Profile(name);
+    }
+
+    Profile[] findAll() {
+        string profilesDir = getProfilesDir();
+        if (!exists(profilesDir)) return [];
+        Profile[] profiles;
+        foreach (DirEntry entry; dirEntries(profilesDir, SpanMode.shallow, false)) {
+            import std.string : endsWith;
+            const suffix = ".sqlite";
+            if (endsWith(entry.name, suffix)) {
+                string profileName = baseName(entry.name, suffix);
+                profiles ~= new Profile(profileName);
+            }
+        }
+        import std.algorithm.sorting : sort;
+        sort(profiles);
+        return profiles;
+    }
+
+    void deleteByName(string name) {
+        string path = getProfilePath(name);
+        if (exists(path)) {
+            std.file.remove(path);
+        }
+    }
+
+    ProfileDataSource getDataSource(in Profile profile) {
+        return new SqliteProfileDataSource(getProfilePath(profile.name));
+    }
+
+    private string getProfilesDir() {
+        return buildPath(this.usersDir, username, "profiles");
+    }
+
+    private string getProfilePath(string name) {
+        return buildPath(this.usersDir, username, "profiles", name ~ ".sqlite");
+    }
+}
+
+class SqlitePropertiesRepository : PropertiesRepository {
+    private Database db;
+    this(Database db) {
+        this.db = db;
+    }
+
+    Optional!string findProperty(string propertyName) {
+        return findOne(
+            db,
+            "SELECT value FROM profile_property WHERE property = ?",
+            r => r.peek!string(0),
+            propertyName
+        );
+        // Statement stmt = this.db.prepare("SELECT value FROM profile_property WHERE property = ?");
+        // stmt.bind(1, propertyName);
+        // ResultRange result = stmt.execute();
+        // if (result.empty) return Optional!string.empty;
+        // return Optional!string.of(result.front.peek!string(0));
+    }
+
+    void setProperty(string name, string value) {
+        if (findProperty(name).isNull) {
+            Statement stmt = this.db.prepare("INSERT INTO profile_property (property, value) VALUES (?, ?)");
+            stmt.bind(1, name);
+            stmt.bind(2, value);
+            stmt.execute();
+        } else {
+            Statement stmt = this.db.prepare("UPDATE profile_property SET value = ? WHERE property = ?");
+            stmt.bind(1, value);
+            stmt.bind(2, name);
+            stmt.execute();
+        }
+    }
+
+    void deleteProperty(string name) {
+        Statement stmt = this.db.prepare("DELETE FROM profile_property WHERE property = ?");
+        stmt.bind(1, name);
+        stmt.execute();
+    }
+
+    ProfileProperty[] findAll() {
+        Statement stmt = this.db.prepare("SELECT * FROM profile_property ORDER BY property ASC");
+        ResultRange result = stmt.execute();
+        ProfileProperty[] props;
+        foreach (Row row; result) {
+            ProfileProperty prop;
+            prop.property = row.peek!string("property");
+            prop.value = row.peek!string("value");
+            props ~= prop;
+        }
+        return props;
+    }
+}
+
+/**
+ * An SQLite implementation of the ProfileDataSource that uses a single
+ * database connection to initialize various entity data access objects lazily.
+ */
+class SqliteProfileDataSource : ProfileDataSource {
+    import account.data;
+    import account.data_impl_sqlite;
+
+    const SCHEMA = import("schema.sql");
+    private const string dbPath;
+    private Database db;
+
+    this(string path) {
+        this.dbPath = path;
+        import std.file : exists;
+        bool needsInit = !exists(path);
+        this.db = Database(path);
+        if (needsInit) {
+            infoF!"Initializing database: %s"(dbPath);
+            db.run(SCHEMA);
+        }
+    }
+
+    PropertiesRepository getPropertiesRepository() {
+        return new SqlitePropertiesRepository(db);
+    }
+
+    AccountRepository getAccountRepository() {
+        return new SqliteAccountRepository(db);
+    }
+}
diff --git a/finnow-api/source/profile/model.d b/finnow-api/source/profile/model.d
new file mode 100644
index 0000000..7952f8a
--- /dev/null
+++ b/finnow-api/source/profile/model.d
@@ -0,0 +1,28 @@
+module profile.model;
+
+import profile.data;
+
+/**
+ * A profile is a complete set of Finnow financial data, all stored in one
+ * single database file. The profile's name is used to lookup the database
+ * partition for its data. A user may own multiple profiles.
+ */
+class Profile {
+    string name;
+
+    this(string name) {
+        this.name = name;
+    }
+
+    override int opCmp(Object other) const {
+        if (Profile p = cast(Profile) other) {
+            return this.name < p.name;
+        }
+        return 1;
+    }
+}
+
+struct ProfileProperty {
+    string property;
+    string value;
+}
diff --git a/finnow-api/source/profile/package.d b/finnow-api/source/profile/package.d
new file mode 100644
index 0000000..c087ff7
--- /dev/null
+++ b/finnow-api/source/profile/package.d
@@ -0,0 +1,6 @@
+/**
+ * This module defines all components pertaining to "Profiles", that is,
+ * isolated Finnow databases that belong to a single user. Each profile is
+ * completely separate from all others.
+ */
+module profile;
diff --git a/finnow-api/source/profile/service.d b/finnow-api/source/profile/service.d
new file mode 100644
index 0000000..3fec1ff
--- /dev/null
+++ b/finnow-api/source/profile/service.d
@@ -0,0 +1,85 @@
+module profile.service;
+
+import handy_httpd;
+import handy_httpd.components.optional;
+
+import profile.model;
+import profile.data;
+import profile.data_impl_sqlite;
+import auth.model;
+
+/**
+ * Validates a profile name.
+ * Params:
+ *   name = The name to check.
+ * Returns: True if the profile name is valid.
+ */
+bool validateProfileName(string name) {
+    import std.regex;
+    import std.uni : toLower;
+    if (name is null || name.length < 3) return false;
+    auto r = ctRegex!(`^[a-zA-Z]+[a-zA-Z0-9_]+$`);
+    return !matchFirst(name, r).empty;
+}
+
+/// Contextual information that's available when handling requests under a profile.
+struct ProfileContext {
+    const Profile profile;
+    const User user;
+}
+
+/**
+ * Tries to get a profile context from a request context. This will attempt to
+ * extract a "profile" path parameter and the authenticated user, and combine
+ * them into the ProfileContext.
+ * Params:
+ *   ctx = The request context to read.
+ * Returns: An optional profile context.
+ */
+Optional!ProfileContext getProfileContext(in HttpRequestContext ctx) {
+    import auth.service : AuthContext, getAuthContext;
+    if ("profile" !in ctx.request.pathParams) return Optional!ProfileContext.empty;
+    string profileName = ctx.request.pathParams["profile"];
+    if (!validateProfileName(profileName)) return Optional!ProfileContext.empty;
+    AuthContext authCtx = getAuthContext(ctx);
+    if (authCtx is null) return Optional!ProfileContext.empty;
+    User user = authCtx.user;
+    ProfileRepository repo = new FileSystemProfileRepository(user.username);
+    return repo.findByName(profileName)
+        .mapIfPresent!(p => ProfileContext(p, user));
+}
+
+/**
+ * Similar to `getProfileContext`, but throws an HttpStatusException with a
+ * 404 NOT FOUND status if no profile context could be obtained.
+ * Params:
+ *   ctx = The request context to read.
+ * Returns: The profile context that was obtained.
+ */
+ProfileContext getProfileContextOrThrow(in HttpRequestContext ctx) {
+    return getProfileContext(ctx).orElseThrow(() => new HttpStatusException(HttpStatus.NOT_FOUND));
+}
+
+/**
+ * Obtains a ProfileDataSource from a ProfileContext. Use this to get access
+ * to all profile data when handling an HTTP request, for example.
+ * Params:
+ *   pc = The profile context.
+ * Returns: The profile data source.
+ */
+ProfileDataSource getProfileDataSource(in ProfileContext pc) {
+    ProfileRepository profileRepo = new FileSystemProfileRepository(pc.user.username);
+    return profileRepo.getDataSource(pc.profile);
+}
+
+/**
+ * Obtains a ProfileDataSource from an HTTP request context. Use this to
+ * access all profile data when handling the request.
+ * Params:
+ *   ctx = The request context.
+ * Returns: The profile data source.
+ */
+ProfileDataSource getProfileDataSource(in HttpRequestContext ctx) {
+    ProfileContext pc = getProfileContextOrThrow(ctx);
+    return getProfileDataSource(pc);
+}
diff --git a/finnow-api/source/model/transaction.d b/finnow-api/source/transaction/model.d
similarity index 86%
rename from finnow-api/source/model/transaction.d
rename to finnow-api/source/transaction/model.d
index a065bf7..3e0e65c 100644
--- a/finnow-api/source/model/transaction.d
+++ b/finnow-api/source/transaction/model.d
@@ -1,7 +1,8 @@
-module model.transaction;
+module transaction.model;
 
 import std.datetime;
-import model.currency;
+
+import money.currency;
 
 struct TransactionVendor {
     ulong id;
@@ -25,9 +26,9 @@ struct Transaction {
     ulong id;
     SysTime timestamp;
     SysTime addedAt;
-    string amount;
+    ulong amount;
     Currency currency;
     string description;
     ulong vendorId;
     ulong categoryId;
-}
+}
\ No newline at end of file
diff --git a/finnow-api/source/util/sqlite.d b/finnow-api/source/util/sqlite.d
new file mode 100644
index 0000000..e866383
--- /dev/null
+++ b/finnow-api/source/util/sqlite.d
@@ -0,0 +1,94 @@
+module util.sqlite;
+
+import slf4d;
+import handy_httpd.components.optional;
+import d2sqlite3;
+
+/**
+ * Tries to find a single row from a database.
+ * Params:
+ *   db = The database to use.
+ *   query = The query to execute.
+ *   resultMapper = A function to map rows to the desired result type.
+ *   args = Arguments for the query.
+ * Returns: An optional result.
+ */
+Optional!T findOne(T, Args...)(Database db, string query, T function(Row) resultMapper, Args args) {
+    Statement stmt = db.prepare(query);
+    stmt.bindAll(args);
+    ResultRange result = stmt.execute();
+    if (result.empty) return Optional!T.empty;
+    return Optional!T.of(resultMapper(result.front));
+}
+
+/**
+ * Finds a list of records from a database.
+ * Params:
+ *   db = The database to use.
+ *   query = The query to execute.
+ *   resultMapper = A function to map rows to the desired result type.
+ *   args = Arguments for the query.
+ * Returns: A list of results.
+ */
+T[] findAll(T, Args...)(Database db, string query, T function(Row) resultMapper, Args args) {
+    Statement stmt = db.prepare(query);
+    stmt.bindAll(args);
+    import std.algorithm : map;
+    import std.array : array;
+    return stmt.execute().map!(r => resultMapper(r)).array;
+}
+
+/**
+ * Determines if at least one record exists.
+ * Params:
+ *   db = The database to use.
+ *   query = The query to execute.
+ *   args = The arguments for the query.
+ * Returns: True if at least one record is returned, or false if not.
+ */
+bool exists(Args...)(Database db, string query, Args args) {
+    Statement stmt = db.prepare(query);
+    stmt.bindAll(args);
+    return !stmt.execute().empty();
+}
+
+/**
+ * Performs an update (UPDATE/INSERT/DELETE).
+ * Params:
+ *   db = The database to use.
+ *   query = The query to execute.
+ *   args = The arguments for the query.
+ * Returns: The number of rows that were affected.
+ */
+int update(Args...)(Database db, string query, Args args) {
+    Statement stmt = db.prepare(query);
+    stmt.bindAll(args);
+    stmt.execute();
+    return db.changes();
+}
+
+/**
+ * Wraps a given delegate block of code in an SQL transaction, so that all
+ * operations will be committed at once when done. If an exception is thrown,
+ * then the changes will be rolled back.
+ * Params:
+ *   db = The database to use.
+ *   dg = The delegate block of code to run in the transaction.
+ * Returns: The return value of the delegate.
+ */
+T doTransaction(T)(Database db, T delegate() dg) {
+    try {
+        db.begin();
+        static if (is(T : void)) {
+            dg();
+        } else {
+            T result = dg();
+        }
+        db.commit();
+        static if (!is(T : void)) return result;
+    } catch (Exception e) {
+        error("Rolling back transaction due to exception.", e);
+        db.rollback();
+        throw e;
+    }
+}