How do I prevent database abuse?
Last checked 31 Aug 2026
Short answer
Combine row-level security with rate limiting on writes, input validation, and CAPTCHA or similar checks on public forms — RLS stops unauthorised reads/writes, but it doesn't stop a legitimate-looking user from hammering an endpoint.
Two different problems
Row-level security controls who can access which rows — it doesn't control how often someone can call an endpoint. Preventing abuse (spam submissions, scraping, cost-driving traffic) needs additional layers on top of correct RLS.
Layers to add
- RLS first — confirm every table only allows the access it should (see /questions/how-do-i-check-supabase-rls). This is the baseline, not the whole solution.
- Rate limiting on public write endpoints (sign-ups, form submissions, comments) — see /questions/how-do-i-rate-limit-an-api.
- Input validation — reject malformed or oversized payloads before they reach the database.
- CAPTCHA or similar on public forms that don't require login, to cut down scripted submissions — see /questions/how-do-i-stop-bots.
- Database constraints — length limits, foreign key checks and
NOT NULLconstraints stop malformed data even if application logic has a gap.
A prompt that helps
Add rate limiting to the public contact form's Edge Function, capped per IP address, and add basic length/format validation before any insert.
What usually goes wrong
Teams treat RLS as covering abuse prevention because it's the security feature they set up — RLS answers "is this user allowed to touch this row," not "is this request part of a spam flood." Both layers are needed together, and for a public app expecting real traffic, budget for rate limiting from day one rather than adding it after an incident.
Sources
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