Supabase Database Essentials

Why Supabase?

Supabase is PostgreSQL with a developer-friendly interface. It includes authentication, real-time subscriptions, and RLS out of the box.

Perfect for Next.js apps, Supabase scales from MVP to millions of users.

Understanding Tables & Relationships

Basic Table Design

Users have many projects. Projects have many tasks. Design tables to reflect these relationships:

• users (id, email, created_at)
• projects (id, user_id, title, created_at)
• tasks (id, project_id, title, status)

Foreign Keys

Link tables with foreign keys. Supabase enforces referential integrity automatically.

Row-Level Security (RLS)

What is RLS?

RLS ensures users can only access their own data at the database level. Even if someone hacks your API, they can't access other users' data.

Setting Up RLS Policies

For a projects table owned by users:

• CREATE POLICY "Users can select their own projects" ON projects FOR SELECT USING (auth.uid() = user_id)
• CREATE POLICY "Users can insert their own projects" ON projects FOR INSERT WITH CHECK (auth.uid() = user_id)
• CREATE POLICY "Users can update their own projects" ON projects FOR UPDATE USING (auth.uid() = user_id)
• CREATE POLICY "Users can delete their own projects" ON projects FOR DELETE USING (auth.uid() = user_id)

Testing RLS

Always test RLS policies. Log in as different users and verify they can't access each other's data.

Authentication

Email/Password Auth

Use Supabase Auth built-in. Call auth.signUp() and auth.signIn() from your frontend.

OAuth Integration

Enable Google, GitHub, or other providers. Users can sign in with a single click.

Sessions

Supabase manages sessions automatically. Store JWT in localStorage or cookies. It expires after 1 hour (configurable).

Real-Time Subscriptions

Listen for Changes

Subscribe to real-time updates on specific tables. When anyone updates a project, all connected clients get notified instantly.

Use Cases

• Live collaboration (Figma-like apps)
• Real-time notifications
• Live dashboards
• Chat systems

Best Practices

Always Use RLS

Never rely on API logic alone. Always enforce security at the database level.

Index Frequently Queried Columns

Create indexes on user_id, project_id, and other columns used in WHERE clauses. This dramatically speeds up queries.

Backup Regularly

Supabase includes daily backups. But set up automated exports to a secure location.

Monitor Performance

Use Supabase logs to identify slow queries. Add indexes to fix bottlenecks.

Ready to Build

Start with a simple schema. Add RLS policies. Test thoroughly. You're now building secure, scalable backends.