Supabase Security: RLS Policies That Scale

Essential RLS Patterns

User Data Isolation

-- Enable RLS
ALTER TABLE posts ENABLE ROW LEVEL SECURITY;

-- Users can only see their own posts
CREATE POLICY "users_own_posts" ON posts
  FOR SELECT USING (auth.uid() = user_id);

-- Users can update their own posts
CREATE POLICY "users_update_own" ON posts
  FOR UPDATE USING (auth.uid() = user_id);

Multi-Tenant SaaS Pattern

-- Helper function
CREATE FUNCTION auth.user_org_id() RETURNS UUID AS $$
  SELECT org_id FROM users WHERE id = auth.uid()
$$ LANGUAGE SQL STABLE;

-- Org-level isolation
CREATE POLICY "org_isolation" ON customers
  FOR SELECT USING (org_id = auth.user_org_id());

Performance Optimization

Always Index RLS Columns

CREATE INDEX idx_posts_user_id ON posts(user_id);
CREATE INDEX idx_customers_org_id ON customers(org_id);

Security Checklist

✓ Enable RLS on ALL tables (no exceptions)
✓ Test policies with different user roles
✓ Never expose service role key on client
✓ Use helper functions to avoid subqueries
✓ Monitor policy performance with EXPLAIN ANALYZE

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