Soft delete with RLS: do I really need `deleted_at is null` in every query?

Put it in the select policy, then no query can forget it:

create policy "own active projects" on public.projects
  for select to authenticated
  using ((select auth.uid()) = owner_id and deleted_at is null);

Catch: once the row is soft deleted, it's invisible to its owner, so update ... set deleted_at = null for undo finds nothing. Do the undo through a small security definer function that checks ownership and restores it, or add a separate policy that lets owners see their own deleted rows only from a "trash" page (e.g. a view with security_invoker).

Different take: a projects_active view with security_invoker = true and where deleted_at is null, and the app only reads from the view. Keeps the policy simple and the trash page can read the table. Both work, it's taste.

Also add a partial index on projects (owner_id) where deleted_at is null, otherwise the filter gets slower as the trash grows.