diff --git a/app.py b/app.py
index 8f839bd..330bb60 100644
--- a/app.py
+++ b/app.py
@@ -66,13 +66,13 @@ def api_register():
     password_hash = auth.hash_password(password)
     user = database.create_user(username, password_hash)
 
-    session["user_id"] = user.doc_id
+    session["user_id"] = user["id"]
     session["username"] = username
 
     return jsonify({
         "success": True,
         "message": "Registration successful",
-        "user_id": user.doc_id
+        "user_id": user["id"]
     }), 201
 
 
@@ -89,14 +89,14 @@ def api_login():
     if not user or not auth.check_password(password, user["password_hash"]):
         return jsonify({"success": False, "message": "Invalid credentials"}), 401
 
-    session["user_id"] = user.doc_id
+    session["user_id"] = user["id"]
     session["username"] = username
 
     return jsonify({
         "success": True,
         "message": "Login successful",
         "user": {
-            "user_id": user.doc_id,
+            "user_id": user["id"],
             "username": user["username"],
             "role": user["role"],
             "max_goals": user["max_goals"]
@@ -118,7 +118,7 @@ def api_me():
     if not user:
         return jsonify({"success": False, "message": "User not found"}), 404
     return jsonify({
-        "user_id": user.doc_id,
+        "user_id": user["id"],
         "username": user["username"],
         "role": user["role"],
         "max_goals": user["max_goals"]
@@ -133,7 +133,7 @@ def api_get_goals():
     result = []
     for goal in goals:
         goal_dict = dict(goal)
-        goal_dict["id"] = goal.doc_id
+        goal_dict["id"] = goal["id"]
         result.append(goal_dict)
     return jsonify(result)
 
@@ -157,7 +157,7 @@ def api_create_goal():
         }), 400
 
     goal = database.create_goal(user_id, title)
-    return jsonify({"success": True, "goal_id": goal.doc_id}), 201
+    return jsonify({"success": True, "goal_id": goal["id"]}), 201
 
 
 @app.route("/api/goals/<int:goal_id>", methods=["PUT"])
@@ -221,7 +221,7 @@ def api_get_tasks():
     result = []
     for task in tasks:
         task_dict = dict(task)
-        task_dict["id"] = task.doc_id
+        task_dict["id"] = task["id"]
         result.append(task_dict)
     return jsonify(result)
 
@@ -245,7 +245,7 @@ def api_create_task():
         return jsonify({"success": False, "message": "Cannot add task to deactivated goal"}), 400
 
     task = database.create_task(goal_id, title, desc)
-    return jsonify({"success": True, "task_id": task.doc_id}), 201
+    return jsonify({"success": True, "task_id": task["id"]}), 201
 
 
 @app.route("/api/tasks/<int:task_id>", methods=["PUT"])
@@ -313,11 +313,11 @@ def api_update_task_status(task_id):
         doing_task = None
         all_tasks = database.get_tasks_by_goal(task["goal_id"])
         for t in all_tasks:
-            if t.get("status") == "doing" and t.doc_id != task.doc_id:
+            if t.get("status") == "doing" and t["id"] != task["id"]:
                 doing_task = t
                 break
         if doing_task:
-            database.update_task(doing_task.doc_id, status="todo")
+            database.update_task(doing_task["id"], status="todo")
         updates["start_time"] = datetime.now().isoformat()
     else:
         updates["start_time"] = None
@@ -359,7 +359,7 @@ def api_get_users():
     result = []
     for user in users:
         result.append({
-            "user_id": user.doc_id,
+            "user_id": user["id"],
             "username": user["username"],
             "role": user["role"],
             "max_goals": user["max_goals"]
diff --git a/config.py b/config.py
index e8f1ecb..fe333b1 100644
--- a/config.py
+++ b/config.py
@@ -1,6 +1,6 @@
 import os
 
-DB_PATH = os.path.join(os.path.dirname(__file__), "data", "db.json")
+DB_PATH = os.path.join(os.path.dirname(__file__), "data", "db.sqlite")
 
 DEFAULT_ADMIN_USERNAME = "admin"
 DEFAULT_ADMIN_PASSWORD = "admin123"
diff --git a/database.py b/database.py
index b028a43..994727c 100644
--- a/database.py
+++ b/database.py
@@ -1,137 +1,219 @@
-import os
-from tinydb import TinyDB, Query
-from tinydb.operations import increment
-import config
+from schema import get_connection
 
-os.makedirs(os.path.dirname(config.DB_PATH), exist_ok=True)
 
-db = TinyDB(config.DB_PATH)
-
-users_table = db.table("users")
-goals_table = db.table("goals")
-tasks_table = db.table("tasks")
-
-User = Query()
-Goal = Query()
-Task = Query()
+def row_to_dict(row):
+    if row is None:
+        return None
+    return dict(row)
 
 
 def init_db():
-    if users_table.count(User.role == "admin") == 0:
-        import bcrypt
-        password_hash = bcrypt.hashpw(
-            config.DEFAULT_ADMIN_PASSWORD.encode("utf-8"),
-            bcrypt.gensalt()
-        ).decode("utf-8")
-        users_table.insert({
-            "username": config.DEFAULT_ADMIN_USERNAME,
-            "password_hash": password_hash,
-            "role": "admin",
-            "max_goals": 100
-        })
+    from schema import init_db as _init_db, migrate_from_tinydb
+    _init_db()
+    migrate_from_tinydb()
 
 
 def get_user_by_username(username):
-    result = users_table.search(User.username == username)
-    return result[0] if result else None
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM users WHERE username = ?", (username,))
+        return row_to_dict(cur.fetchone())
+    finally:
+        conn.close()
 
 
 def get_user_by_id(user_id):
-    return users_table.get(doc_id=user_id)
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM users WHERE id = ?", (user_id,))
+        return row_to_dict(cur.fetchone())
+    finally:
+        conn.close()
 
 
 def create_user(username, password_hash, role="user", max_goals=None):
     if max_goals is None:
-        max_goals = config.DEFAULT_MAX_GOALS
-    doc_id = users_table.insert({
-        "username": username,
-        "password_hash": password_hash,
-        "role": role,
-        "max_goals": max_goals
-    })
-    return users_table.get(doc_id=doc_id)
+        max_goals = 5
+    conn = get_connection()
+    try:
+        cur = conn.execute(
+            "INSERT INTO users (username, password_hash, role, max_goals) VALUES (?, ?, ?, ?)",
+            (username, password_hash, role, max_goals)
+        )
+        conn.commit()
+        return row_to_dict(conn.execute("SELECT * FROM users WHERE id = ?", (cur.lastrowid,)).fetchone())
+    finally:
+        conn.close()
 
 
 def update_user(user_id, **kwargs):
-    users_table.update(kwargs, doc_ids=[user_id])
+    if not kwargs:
+        return
+    sets = ", ".join(f"{k} = ?" for k in kwargs)
+    values = list(kwargs.values()) + [user_id]
+    conn = get_connection()
+    try:
+        conn.execute(f"UPDATE users SET {sets} WHERE id = ?", values)
+        conn.commit()
+    finally:
+        conn.close()
 
 
 def get_all_users():
-    return users_table.all()
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM users")
+        return [row_to_dict(r) for r in cur.fetchall()]
+    finally:
+        conn.close()
 
 
 def get_goals_by_user(user_id):
-    return goals_table.search(Goal.user_id == user_id)
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM goals WHERE user_id = ?", (user_id,))
+        return [row_to_dict(r) for r in cur.fetchall()]
+    finally:
+        conn.close()
 
 
 def get_goal_by_id(goal_id):
-    return goals_table.get(doc_id=goal_id)
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM goals WHERE id = ?", (goal_id,))
+        return row_to_dict(cur.fetchone())
+    finally:
+        conn.close()
 
 
 def create_goal(user_id, title):
-    doc_id = goals_table.insert({
-        "user_id": user_id,
-        "title": title,
-        "activated": True
-    })
-    return goals_table.get(doc_id=doc_id)
+    conn = get_connection()
+    try:
+        cur = conn.execute(
+            "INSERT INTO goals (user_id, title, activated) VALUES (?, ?, 1)",
+            (user_id, title)
+        )
+        conn.commit()
+        return row_to_dict(conn.execute("SELECT * FROM goals WHERE id = ?", (cur.lastrowid,)).fetchone())
+    finally:
+        conn.close()
 
 
 def update_goal(goal_id, **kwargs):
-    goals_table.update(kwargs, doc_ids=[goal_id])
+    if not kwargs:
+        return
+    sets = ", ".join(f"{k} = ?" for k in kwargs)
+    values = list(kwargs.values()) + [goal_id]
+    conn = get_connection()
+    try:
+        conn.execute(f"UPDATE goals SET {sets} WHERE id = ?", values)
+        conn.commit()
+    finally:
+        conn.close()
 
 
 def delete_goal(goal_id):
-    tasks = tasks_table.search(Task.goal_id == goal_id)
-    for task in tasks:
-        tasks_table.remove(doc_ids=[task.doc_id])
-    goals_table.remove(doc_ids=[goal_id])
+    conn = get_connection()
+    try:
+        conn.execute("DELETE FROM tasks WHERE goal_id = ?", (goal_id,))
+        conn.execute("DELETE FROM goals WHERE id = ?", (goal_id,))
+        conn.commit()
+    finally:
+        conn.close()
 
 
 def count_goals_by_user(user_id):
-    return len(goals_table.search(Goal.user_id == user_id))
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT COUNT(*) FROM goals WHERE user_id = ?", (user_id,))
+        return cur.fetchone()[0]
+    finally:
+        conn.close()
 
 
 def get_tasks_by_goal(goal_id):
-    return tasks_table.search(Task.goal_id == goal_id)
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM tasks WHERE goal_id = ?", (goal_id,))
+        return [row_to_dict(r) for r in cur.fetchall()]
+    finally:
+        conn.close()
 
 
 def get_task_by_id(task_id):
-    return tasks_table.get(doc_id=task_id)
+    conn = get_connection()
+    try:
+        cur = conn.execute("SELECT * FROM tasks WHERE id = ?", (task_id,))
+        return row_to_dict(cur.fetchone())
+    finally:
+        conn.close()
 
 
 def create_task(goal_id, title, desc="", status="todo", order=None):
     if order is None:
-        existing_tasks = tasks_table.search(Task.goal_id == goal_id)
-        unfinished = [t for t in existing_tasks if t.get("status") != "done"]
-        order = max([t.get("order", 0) for t in unfinished], default=0) + 1.0
-    
-    doc_id = tasks_table.insert({
-        "goal_id": goal_id,
-        "title": title,
-        "desc": desc,
-        "status": status,
-        "start_time": None,
-        "finished_time": None,
-        "order": order
-    })
-    return tasks_table.get(doc_id=doc_id)
+        conn = get_connection()
+        try:
+            cur = conn.execute(
+                """SELECT COALESCE(MAX("order"), 0) + 1.0 FROM tasks
+                   WHERE goal_id = ? AND status != 'done'""",
+                (goal_id,)
+            )
+            order = cur.fetchone()[0]
+        finally:
+            conn.close()
+
+    conn = get_connection()
+    try:
+        cur = conn.execute(
+            """INSERT INTO tasks (goal_id, title, desc, status, start_time, finished_time, "order")
+               VALUES (?, ?, ?, ?, ?, ?, ?)""",
+            (goal_id, title, desc, status, None, None, order)
+        )
+        conn.commit()
+        return row_to_dict(conn.execute("SELECT * FROM tasks WHERE id = ?", (cur.lastrowid,)).fetchone())
+    finally:
+        conn.close()
 
 
 def update_task(task_id, **kwargs):
-    tasks_table.update(kwargs, doc_ids=[task_id])
+    if not kwargs:
+        return
+    sets = ", ".join(f"{k} = ?" for k in kwargs)
+    values = list(kwargs.values()) + [task_id]
+    conn = get_connection()
+    try:
+        conn.execute(f"UPDATE tasks SET {sets} WHERE id = ?", values)
+        conn.commit()
+    finally:
+        conn.close()
 
 
 def delete_task(task_id):
-    tasks_table.remove(doc_ids=[task_id])
+    conn = get_connection()
+    try:
+        conn.execute("DELETE FROM tasks WHERE id = ?", (task_id,))
+        conn.commit()
+    finally:
+        conn.close()
 
 
 def get_tasks_sorted(goal_id):
-    all_tasks = tasks_table.search(Task.goal_id == goal_id)
-    unfinished = [t for t in all_tasks if t.get("status") != "done"]
-    finished = [t for t in all_tasks if t.get("status") == "done"]
+    conn = get_connection()
+    try:
+        cur = conn.execute(
+            """SELECT * FROM tasks WHERE goal_id = ? AND status = 'done'
+               ORDER BY finished_time DESC""",
+            (goal_id,)
+        )
+        finished = [row_to_dict(r) for r in cur.fetchall()]
 
-    unfinished.sort(key=lambda t: t.get("order", 0))
-    finished.sort(key=lambda t: t.get("finished_time", ""), reverse=True)
+        cur = conn.execute(
+            """SELECT * FROM tasks WHERE goal_id = ? AND status != 'done'
+               ORDER BY "order" ASC""",
+            (goal_id,)
+        )
+        unfinished = [row_to_dict(r) for r in cur.fetchall()]
 
-    return finished + unfinished
+        return finished + unfinished
+    finally:
+        conn.close()
diff --git a/pyproject.toml b/pyproject.toml
index 92831f9..f26bc42 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,5 +6,4 @@ requires-python = ">=3.13"
 dependencies = [
     "bcrypt>=5.0.0",
     "flask>=3.1.3",
-    "tinydb>=4.8.2",
 ]
diff --git a/schema.py b/schema.py
new file mode 100644
index 0000000..67b1388
--- /dev/null
+++ b/schema.py
@@ -0,0 +1,116 @@
+import sqlite3
+import os
+import json
+import config
+
+
+CREATE_USERS = """
+CREATE TABLE IF NOT EXISTS users (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    username TEXT NOT NULL UNIQUE,
+    password_hash TEXT NOT NULL,
+    role TEXT NOT NULL DEFAULT 'user',
+    max_goals INTEGER NOT NULL DEFAULT 5
+)
+"""
+
+CREATE_GOALS = """
+CREATE TABLE IF NOT EXISTS goals (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL,
+    title TEXT NOT NULL,
+    activated INTEGER NOT NULL DEFAULT 1,
+    FOREIGN KEY (user_id) REFERENCES users(id)
+)
+"""
+
+CREATE_TASKS = """
+CREATE TABLE IF NOT EXISTS tasks (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    goal_id INTEGER NOT NULL,
+    title TEXT NOT NULL,
+    desc TEXT NOT NULL DEFAULT '',
+    status TEXT NOT NULL DEFAULT 'todo',
+    start_time TEXT,
+    finished_time TEXT,
+    "order" REAL NOT NULL DEFAULT 0.0,
+    FOREIGN KEY (goal_id) REFERENCES goals(id)
+)
+"""
+
+
+def get_connection():
+    os.makedirs(os.path.dirname(config.DB_PATH), exist_ok=True)
+    conn = sqlite3.connect(config.DB_PATH)
+    conn.row_factory = sqlite3.Row
+    conn.execute("PRAGMA foreign_keys = ON")
+    return conn
+
+
+def init_db():
+    conn = get_connection()
+    try:
+        conn.execute(CREATE_USERS)
+        conn.execute(CREATE_GOALS)
+        conn.execute(CREATE_TASKS)
+        conn.commit()
+
+        import bcrypt
+        cur = conn.execute("SELECT COUNT(*) FROM users WHERE role = 'admin'")
+        if cur.fetchone()[0] == 0:
+            password_hash = bcrypt.hashpw(
+                config.DEFAULT_ADMIN_PASSWORD.encode("utf-8"),
+                bcrypt.gensalt()
+            ).decode("utf-8")
+            conn.execute(
+                "INSERT INTO users (username, password_hash, role, max_goals) VALUES (?, ?, ?, ?)",
+                (config.DEFAULT_ADMIN_USERNAME, password_hash, "admin", 100)
+            )
+            conn.commit()
+    finally:
+        conn.close()
+
+
+def migrate_from_tinydb():
+    json_path = os.path.join(os.path.dirname(config.DB_PATH), "db.json")
+    if not os.path.exists(json_path):
+        return
+
+    conn = get_connection()
+    try:
+        with open(json_path, "r") as f:
+            data = json.load(f)
+
+        if "users" in data:
+            for doc_id, record in data["users"].items():
+                record["id"] = int(doc_id)
+                if conn.execute("SELECT COUNT(*) FROM users WHERE id = ?", (record["id"],)).fetchone()[0] == 0:
+                    conn.execute(
+                        "INSERT INTO users (id, username, password_hash, role, max_goals) VALUES (?, ?, ?, ?, ?)",
+                        (record["id"], record["username"], record["password_hash"], record["role"], record["max_goals"])
+                    )
+
+        if "goals" in data:
+            for doc_id, record in data["goals"].items():
+                record["id"] = int(doc_id)
+                if conn.execute("SELECT COUNT(*) FROM goals WHERE id = ?", (record["id"],)).fetchone()[0] == 0:
+                    conn.execute(
+                        "INSERT INTO goals (id, user_id, title, activated) VALUES (?, ?, ?, ?)",
+                        (record["id"], record["user_id"], record["title"], 1 if record.get("activated", True) else 0)
+                    )
+
+        if "tasks" in data:
+            for doc_id, record in data["tasks"].items():
+                record["id"] = int(doc_id)
+                if conn.execute("SELECT COUNT(*) FROM tasks WHERE id = ?", (record["id"],)).fetchone()[0] == 0:
+                    conn.execute(
+                        """INSERT INTO tasks (id, goal_id, title, desc, status, start_time, finished_time, "order")
+                           VALUES (?, ?, ?, ?, ?, ?, ?, ?)""",
+                        (record["id"], record["goal_id"], record["title"], record.get("desc", ""),
+                         record.get("status", "todo"), record.get("start_time"), record.get("finished_time"),
+                         record.get("order", 0.0))
+                    )
+
+        conn.commit()
+    finally:
+        conn.close()
diff --git a/static/js/goals.js b/static/js/goals.js
index 96edbe4..ee210c2 100644
--- a/static/js/goals.js
+++ b/static/js/goals.js
@@ -60,7 +60,7 @@ function openModal(goal = null) {
     
     if (goal) {
         modalTitle.textContent = "Edit Goal";
-        goalId.value = goal.doc_id;
+        goalId.value = goal.id;
         goalTitle.value = goal.title;
     } else {
         modalTitle.textContent = "Create Goal";