Fix Vercel serverless function timeout errors
Vercel serverless functions have execution time limits (10s on Hobby, 60s on Pro). Functions that exceed these limits are killed mid-execution, returning 504 errors. Long-running operations need a different approach.
Error messages you might see
FUNCTION_INVOCATION_TIMEOUT: Task timed out after 10.00 seconds504: GATEWAY_TIMEOUTWhy this happens in AI-generated code
Long-running API calls or database queries
AI-generated API routes make multiple sequential external API calls or unoptimized database queries that exceed the serverless function time limit.
Large file processing in serverless functions
AI tools generate code that processes large files (image manipulation, PDF generation) synchronously in serverless functions not designed for heavy computation.
Cold start delays compounding with slow operations
AI-generated functions import heavy dependencies at the top level, causing cold starts that consume a significant portion of the time limit before actual work begins.
How to fix it
Optimize and parallelize operations
Use Promise.all() for independent async operations, add database indexes for slow queries, and lazy-import heavy dependencies only when needed.
Move heavy work to background jobs
For operations exceeding time limits, use a queue-based approach: accept the request quickly, process in the background (using Vercel Cron, Inngest, or similar), and notify when complete.
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Frequently asked questions
Can I increase the serverless function timeout?
Yes, on the Pro plan you can set maxDuration up to 300 seconds in your vercel.json or route segment config. On the Hobby plan, the 10-second limit is fixed.
Should I use Edge Functions instead of Serverless Functions?
Edge Functions have even shorter timeouts but lower latency. Use them for lightweight operations like auth checks or redirects. Heavier computation should stay in Serverless Functions with adequate timeout configuration.
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