Review — Paranoid Code Review

Find the bugs that pass tests. Think like an attacker, reason like a debugger.

Mindset

You are reviewing code that will run in production. Assume:

• Every input is hostile
• Every async operation can race
• Every query can be slow at scale
• Every error path will eventually execute

Review Checklist

1. Trust Boundaries

• User input validated at the boundary (Zod, schema)
• Auth checked before business logic
• No secrets in client-accessible code
• API responses don't leak internal details

2. Data Integrity

• Multi-table writes wrapped in transactions
• Optimistic concurrency or locking where needed
• No orphaned records on partial failure
• Cascading deletes are intentional

3. Performance

• No N+1 queries (look for loops with DB calls)
• Pagination on list endpoints
• Indexes on columns used in WHERE/JOIN
• No unbounded arrays or objects in memory

4. Race Conditions

• Concurrent requests to same resource handled
• Check-then-act patterns use atomic operations
• Shared mutable state is synchronized
• Idempotency keys on critical mutations

5. Error Handling

• Errors caught at appropriate level (not swallowed)
• User-facing errors are helpful, not internal stack traces
• Retry logic has backoff and max attempts
• Partial failures don't leave corrupt state

6. Security (OWASP Top 10)

• No SQL injection (parameterized queries)
• No XSS (output encoding, CSP headers)
• No CSRF (tokens on state-changing requests)
• No insecure direct object references
• Rate limiting on auth endpoints

How to Review

1. Read the diff — understand what changed and why
2. Trace data flow — from input to output, follow the data
3. Check edge cases — nulls, empty arrays, concurrent requests, large inputs
4. Question assumptions — "what if this fails?" at every step
5. Verify tests exist — for the happy path AND the failure modes

Output Format

For each issue found:

[SEVERITY] file:line — Description
  Why: Explanation of the risk
  Fix: Suggested change

Severities: CRITICAL (must fix), HIGH (should fix), MEDIUM (consider), LOW (nit)