Supabase RLS Deep Dive — Multi-Tenant Design, Dynamic Policies, and Performance

Row Level Security (RLS) is the foundation of safe multi-user Supabase apps. This post goes beyond "just enable it" — covering multi-tenant architecture, dynamic policies, JWT claims, and performance tuning from a production codebase.

RLS Basics

-- Enable RLS on the table ALTER TABLE tasks ENABLE ROW LEVEL SECURITY ;

-- SELECT: users see only their own rows CREATE POLICY "users_own_tasks_select" ON tasks FOR SELECT USING ( auth . uid () = user_id );

-- INSERT: enforce correct user_id CREATE POLICY "users_own_tasks_insert" ON tasks FOR INSERT WITH CHECK ( auth . uid () = user_id );

-- UPDATE CREATE POLICY "users_own_tasks_update" ON tasks FOR UPDATE USING ( auth . uid () = user_id ) WITH CHECK ( auth . uid () = user_id );

-- DELETE CREATE POLICY "users_own_tasks_delete" ON tasks FOR DELETE USING ( auth .…