Developer finds Claude Code's non-atomic Prisma schema causes race condition on concurrent signups

The developer reported on Reddit that Claude Code generated a 'create workspace on signup' flow that worked perfectly in solo testing. However, during a soft launch with two users signing up at the same time, foreign key constraint errors occurred. The root cause was a non-atomic pattern: first create the workspace, then link the user to it as separate steps. Under concurrent requests, the second user's link step could reference a workspace not yet committed by the first user's creation step. The fix involved swapping to an atomic operation (e.g., using Prisma's nested create or a transaction). This incident underscores that AI-generated code can introduce subtle concurrency bugs that only surface under real-world load.