TL;DR
Supabase uses Row Level Security (RLS) at the PostgreSQL level, while Convex uses TypeScript functions with built-in validation. Supabase's security is declarative (SQL policies), Convex's is imperative (code). Both are secure when properly implemented. Supabase has a steeper learning curve but more mature security model. Convex is easier to reason about with TypeScript familiarity.
Architecture Comparison
Supabase and Convex take fundamentally different approaches to building backends:
| Feature | Supabase | Convex |
|---|---|---|
| Database | PostgreSQL | Custom document DB |
| Security Model | Row Level Security (SQL) | Function-level auth checks |
| Query Language | SQL via client or REST | TypeScript functions |
| Real-time | Postgres LISTEN/NOTIFY | Built-in reactive queries |
| Direct DB Access | Yes (with RLS) | No (functions only) |
Security Model
Supabase: Row Level Security
Supabase exposes your PostgreSQL database directly to the frontend. Security is handled by RLS policies:
- Policies are SQL statements that filter rows
- Evaluated on every query automatically
- Uses
auth.uid()to identify the current user - Must be explicitly enabled on each table
- Policies can reference other tables for complex logic
Warning: RLS is disabled by default in Supabase. Without enabling it, your anon key gives full read/write access to all data in that table.
Convex: Function-Based Security
Convex doesn't expose the database directly. All access goes through TypeScript functions:
- Queries and mutations are TypeScript functions you write
- Authentication context available in every function
- Validation with Zod-like schema validation
- No direct database access from client
- Security logic is regular code, not a DSL
Convex Approach: Since clients can only call your functions (not run arbitrary queries), security is enforced by the code you write in those functions. Forget to check auth? That specific function is vulnerable.
Authentication
| Feature | Supabase | Convex |
|---|---|---|
| Built-in Auth | Supabase Auth | Clerk, Auth0, custom |
| Auth in Security Rules | auth.uid() in RLS | ctx.auth in functions |
| Social Login | Google, GitHub, etc. | Via auth provider |
| Anonymous Auth | Yes | Provider-dependent |
Supabase has built-in authentication tightly integrated with RLS. Convex relies on external auth providers but provides clean integration with services like Clerk.
Common Security Patterns
User Data Isolation
Supabase: Create an RLS policy checking auth.uid() = user_id. This runs automatically on every query to that table.
Convex: Check ctx.auth.userId in your query function and filter results accordingly. You're responsible for adding this check to every function that needs it.
Admin Access
Supabase: Create a function that checks a roles table, then use it in RLS policies. Or use the service role key server-side (bypasses RLS).
Convex: Check user role in your function code. Internal functions can bypass auth checks for server-to-server operations.
Error Handling and Information Disclosure
| Aspect | Supabase | Convex |
|---|---|---|
| Permission Denied | Empty result set | Thrown error |
| Missing Data | Empty result (can't distinguish) | Customizable response |
| Error Details | PostgreSQL errors | Your error messages |
With RLS, unauthorized queries silently return empty results. This prevents information disclosure but can make debugging harder. Convex lets you control error handling explicitly.
Testing Security
Supabase
- Test RLS policies in SQL editor with different roles
- Use Supabase client in tests with test users
- Check policies return expected results for each scenario
Convex
- Unit test functions with mocked auth context
- Integration tests with test accounts
- TypeScript catches many issues at compile time
Which Should You Choose?
Choose Supabase If:
You're comfortable with SQL and PostgreSQL, want database-level security guarantees, need complex relational queries, or prefer declarative security policies that can't be bypassed by buggy code.
Choose Convex If:
You prefer TypeScript over SQL, want security logic in regular code, need reactive real-time features as a core part of your app, or find RLS policies confusing compared to function-based auth checks.
Which is more secure by default?
Convex is arguably more secure by default because clients can only call your functions, not run arbitrary queries. Supabase with RLS disabled exposes all data. However, both platforms are equally secure when properly configured.
Can I use SQL with Convex?
No. Convex uses its own query API through TypeScript functions. If you need SQL capabilities or want to use PostgreSQL features, Supabase is the better choice.
What if I forget to add auth checks in Convex?
That specific function would be unprotected. Unlike RLS which applies to all queries on a table, Convex security is per-function. Code review and testing are important to catch missing checks.
Can I switch between Supabase and Convex later?
Switching is significant work. The data models, query patterns, and security implementations are completely different. Choose based on your long-term needs rather than planning to migrate.