diff --git a/src/database/adapter.ts b/src/database/adapter.ts
new file mode 100644
index 0000000..977e613
--- /dev/null
+++ b/src/database/adapter.ts
@@ -0,0 +1,173 @@
+import { createChildLogger } from "../logger";
+import { config } from "../config";
+import * as postgres from "./postgres";
+import * as sqliteModule from "../muxer-queue";
+
+const logger = createChildLogger("db-adapter");
+
+/**
+ * Unified database adapter interface matching SQLite API
+ */
+export interface DatabaseStatement {
+  run: (...params: unknown[]) => { changes: number };
+  all: (...params: unknown[]) => unknown[];
+  get: (...params: unknown[]) => unknown;
+}
+
+export interface DatabaseAdapter {
+  prepare: (sql: string) => DatabaseStatement;
+  exec: (sql: string) => void;
+  close: () => Promise<void>;
+}
+
+/**
+ * PostgreSQL adapter implementing DatabaseAdapter interface
+ */
+class PostgresAdapter implements DatabaseAdapter {
+  prepare(sql: string): DatabaseStatement {
+    // Convert SQLite placeholders (?) to PostgreSQL placeholders ($1, $2, etc.)
+    const pgSql = this.convertPlaceholders(sql);
+
+    return {
+      run: (...params: unknown[]) => {
+        return this.runSync(pgSql, params);
+      },
+      all: (...params: unknown[]) => {
+        return this.allSync(pgSql, params);
+      },
+      get: (...params: unknown[]) => {
+        return this.getSync(pgSql, params);
+      },
+    };
+  }
+
+  exec(sql: string): void {
+    // For PostgreSQL, exec is typically used for schema creation
+    // We'll queue this for execution but note that exec() is synchronous in SQLite
+    // and async in PostgreSQL, so this is a limitation of the adapter
+    logger.warn(
+      "exec() called on PostgreSQL adapter - this is not truly synchronous. Use query() for schema operations.",
+    );
+    // In practice, schema operations should be handled separately via migrations
+  }
+
+  async close(): Promise<void> {
+    await postgres.closePool();
+  }
+
+  /**
+   * Convert SQLite ? placeholders to PostgreSQL $1, $2, etc.
+   */
+  private convertPlaceholders(sql: string): string {
+    let paramIndex = 1;
+    return sql.replace(/\?/g, () => `$${paramIndex++}`);
+  }
+
+  /**
+   * Synchronous wrapper for run() - note: this is a limitation
+   * In production, async operations should be handled properly
+   */
+  private runSync(sql: string, params: unknown[]): { changes: number } {
+    // This is a placeholder - actual implementation would need async handling
+    // For now, we'll throw an error to indicate this needs proper async handling
+    logger.error(
+      "runSync called on PostgreSQL adapter - this operation must be async",
+    );
+    throw new Error(
+      "PostgreSQL adapter requires async operations. Use query() directly instead of prepare().run()",
+    );
+  }
+
+  /**
+   * Synchronous wrapper for all() - note: this is a limitation
+   */
+  private allSync(sql: string, params: unknown[]): unknown[] {
+    logger.error(
+      "allSync called on PostgreSQL adapter - this operation must be async",
+    );
+    throw new Error(
+      "PostgreSQL adapter requires async operations. Use query() directly instead of prepare().all()",
+    );
+  }
+
+  /**
+   * Synchronous wrapper for get() - note: this is a limitation
+   */
+  private getSync(sql: string, params: unknown[]): unknown {
+    logger.error(
+      "getSync called on PostgreSQL adapter - this operation must be async",
+    );
+    throw new Error(
+      "PostgreSQL adapter requires async operations. Use query() directly instead of prepare().get()",
+    );
+  }
+}
+
+/**
+ * SQLite adapter wrapping better-sqlite3
+ */
+class SqliteAdapter implements DatabaseAdapter {
+  private db: sqliteModule.SqliteDatabase;
+
+  constructor(db: sqliteModule.SqliteDatabase) {
+    this.db = db;
+  }
+
+  prepare(sql: string): DatabaseStatement {
+    const stmt = this.db.prepare(sql);
+    return {
+      run: (...params: unknown[]) => stmt.run(...params),
+      all: (...params: unknown[]) => stmt.all(...params),
+      get: (...params: unknown[]) => stmt.get(...params),
+    };
+  }
+
+  exec(sql: string): void {
+    this.db.exec(sql);
+  }
+
+  async close(): Promise<void> {
+    await sqliteModule.closeQueue();
+  }
+}
+
+/**
+ * Get database adapter based on configuration
+ * Returns appropriate adapter (PostgreSQL or SQLite)
+ */
+export async function getDatabase(): Promise<DatabaseAdapter> {
+  if (config.DATABASE_TYPE === "postgres") {
+    logger.info("Initializing PostgreSQL adapter");
+    const pool = postgres.getPool();
+    logger.info(
+      {
+        host: postgres.buildConfig().host,
+        port: postgres.buildConfig().port,
+        database: postgres.buildConfig().database,
+      },
+      "PostgreSQL connection pool initialized",
+    );
+    return new PostgresAdapter();
+  } else {
+    logger.info("Initializing SQLite adapter");
+    const db = sqliteModule.getDatabase();
+    logger.info("SQLite database initialized");
+    return new SqliteAdapter(db);
+  }
+}
+
+/**
+ * Get database adapter synchronously (for SQLite)
+ * Note: This only works for SQLite. PostgreSQL requires async initialization.
+ */
+export function getDatabaseSync(): DatabaseAdapter {
+  if (config.DATABASE_TYPE === "postgres") {
+    logger.warn(
+      "getDatabaseSync called with PostgreSQL - use getDatabase() instead for proper async handling",
+    );
+    return new PostgresAdapter();
+  } else {
+    const db = sqliteModule.getDatabase();
+    return new SqliteAdapter(db);
+  }
+}