diff --git a/backend/package.json b/backend/package.json
index f29e2e1..9a0acbb 100644
--- a/backend/package.json
+++ b/backend/package.json
@@ -12,7 +12,7 @@
     "express": "^4.18.0",
     "sqlite3": "^5.1.0",
     "jsonwebtoken": "^9.0.0",
-    "multer": "^1.4.5",
+    "multer": "^1.4.5-lts.1",
     "bcrypt": "^5.1.0",
     "cors": "^2.8.5"
   },
diff --git a/backend/src/db.js b/backend/src/db.js
index 1947e48..5b1883c 100644
--- a/backend/src/db.js
+++ b/backend/src/db.js
@@ -1,72 +1,86 @@
-// Simple SQLite database wrapper
-// In production, use better-sqlite3 or similar
+// Simple SQLite database wrapper using sqlite3
+const sqlite3 = require('sqlite3').verbose();
 
-const Database = require('better-sqlite3');
-const db = new Database('clouddisk.db');
+const dbPath = process.env.DB_PATH || './clouddisk.db';
+const db = new sqlite3.Database(dbPath);
 
 // Initialize tables
-db.exec(`
-  CREATE TABLE IF NOT EXISTS users (
-    id INTEGER PRIMARY KEY AUTOINCREMENT,
-    username TEXT UNIQUE NOT NULL,
-    password_hash TEXT NOT NULL,
-    email TEXT,
-    storage_used INTEGER DEFAULT 0,
-    storage_limit INTEGER DEFAULT 10737418240,
-    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
-  );
+db.serialize(() => {
+  db.run(`
+    CREATE TABLE IF NOT EXISTS users (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      username TEXT UNIQUE NOT NULL,
+      password_hash TEXT NOT NULL,
+      email TEXT,
+      storage_used INTEGER DEFAULT 0,
+      storage_limit INTEGER DEFAULT 10737418240,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
+    )
+  `);
   
-  CREATE TABLE IF NOT EXISTS files (
-    id INTEGER PRIMARY KEY AUTOINCREMENT,
-    user_id INTEGER NOT NULL,
-    parent_id INTEGER,
-    name TEXT NOT NULL,
-    type TEXT,
-    size INTEGER DEFAULT 0,
-    path TEXT,
-    hash TEXT,
-    is_folder INTEGER DEFAULT 0,
-    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-    deleted_at DATETIME,
-    FOREIGN KEY (user_id) REFERENCES users(id),
-    FOREIGN KEY (parent_id) REFERENCES files(id)
-  );
+  db.run(`
+    CREATE TABLE IF NOT EXISTS files (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      user_id INTEGER NOT NULL,
+      parent_id INTEGER,
+      name TEXT NOT NULL,
+      type TEXT,
+      size INTEGER DEFAULT 0,
+      path TEXT,
+      hash TEXT,
+      is_folder INTEGER DEFAULT 0,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      deleted_at DATETIME,
+      FOREIGN KEY (user_id) REFERENCES users(id),
+      FOREIGN KEY (parent_id) REFERENCES files(id)
+    )
+  `);
   
-  CREATE TABLE IF NOT EXISTS shares (
-    id INTEGER PRIMARY KEY AUTOINCREMENT,
-    file_id INTEGER NOT NULL,
-    share_token TEXT UNIQUE NOT NULL,
-    password TEXT,
-    expires_at DATETIME,
-    view_count INTEGER DEFAULT 0,
-    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (file_id) REFERENCES files(id)
-  );
+  db.run(`
+    CREATE TABLE IF NOT EXISTS shares (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      file_id INTEGER NOT NULL,
+      share_token TEXT UNIQUE NOT NULL,
+      password TEXT,
+      expires_at DATETIME,
+      view_count INTEGER DEFAULT 0,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      FOREIGN KEY (file_id) REFERENCES files(id)
+    )
+  `);
   
-  CREATE TABLE IF NOT EXISTS sync_logs (
-    id INTEGER PRIMARY KEY AUTOINCREMENT,
-    user_id INTEGER NOT NULL,
-    file_id INTEGER,
-    action TEXT,
-    status TEXT,
-    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (user_id) REFERENCES users(id)
-  );
-`);
+  db.run(`
+    CREATE TABLE IF NOT EXISTS sync_status (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      user_id INTEGER NOT NULL,
+      last_sync_time DATETIME,
+      status TEXT DEFAULT 'idle',
+      total_files INTEGER DEFAULT 0,
+      synced_files INTEGER DEFAULT 0,
+      FOREIGN KEY (user_id) REFERENCES users(id)
+    )
+  `);
+});
 
-module.exports = db;
+// Wrapper functions to match the old API
+const query = (sql, params = []) => {
+  return new Promise((resolve, reject) => {
+    db.all(sql, params, (err, rows) => {
+      if (err) reject(err);
+      else resolve(rows);
+    });
+  });
+};
 
-// Sync tables (for reference - would be in migration in production)
-db.exec(`
-  CREATE TABLE IF NOT EXISTS sync_status (
-    id INTEGER PRIMARY KEY AUTOINCREMENT,
-    user_id INTEGER NOT NULL,
-    last_sync_time DATETIME,
-    status TEXT DEFAULT 'idle',
-    total_files INTEGER DEFAULT 0,
-    synced_files INTEGER DEFAULT 0,
-    FOREIGN KEY (user_id) REFERENCES users(id)
-  );
-`);
+const run = (sql, params = []) => {
+  return new Promise((resolve, reject) => {
+    db.run(sql, params, function(err) {
+      if (err) reject(err);
+      else resolve({ lastInsertRowid: this.lastID, changes: this.changes });
+    });
+  });
+};
+
+module.exports = { query, run, db };