Why AI-Built Apps Feel Fast in Testing and Break in Production

Short summary

A founder shipped a Bolt.new-built reporting tool that worked perfectly until 80 concurrent users exposed four structural issues: missing database indexes, under-configured connection pools, N+1 queries, and cold starts. These problems are structurally invisible at small scale because AI coding tools generate correct code but don't optimize for concurrent load. The key lesson: correct and performant are identical at ten users but very different at five hundred.

• •AI tools write correct code but don't optimize for concurrent load
• •Four scaling issues found: missing indexes, small connection pool, N+1 queries, cold starts
• •Problems are structurally invisible during solo testing — they only emerge under concurrent user load

Generated with AI, which can make mistakes.