Vercel 500 FUNCTION_INVOCATION_FAILED Error

Symptoms

Pages or API routes return '500: INTERNAL_SERVER_ERROR' with code FUNCTION_INVOCATION_FAILED, often working locally but failing on Vercel.

Why it happens

• Uncaught exception or unhandled promise rejection
• Environment variable missing in Production or Preview
• Native dependency that does not work in the function runtime
• Database connection errors or too many open connections (1,024 file descriptor limit)
• Running out of function memory

How to fix it

Try these in order — the most common fix is first.

1. 1. Read the stack trace

   1. Project > Logs, filter by status 500
   2. Open the request to see the error and file/line
   3. Hobby keeps runtime logs for only 1 hour, so reproduce and check quickly

2. 2. Catch errors

   1. Wrap handlers in try/catch and return an error Response
   2. Await or .catch() every promise, including fire-and-forget calls

3. 3. Check configuration

   1. Confirm all required environment variables exist for the environment you are testing
   2. Redeploy after adding them
   3. Use connection pooling for databases and close connections

4. 4. Increase memory (Pro)

   1. Settings > Functions > default memory (up to 4 GB on Pro)
   2. Redeploy and monitor

This guide also covers

• vercel function_invocation_failed
• vercel 500 internal server error
• vercel serverless function crashed
• vercel api route 500

Other Vercel errors

• Vercel Deployment Failed: Build Error
• Vercel 404 NOT_FOUND After Deploy
• Vercel FUNCTION_INVOCATION_TIMEOUT (504) Error
• Vercel Build Exceeded Memory (SIGKILL / Out of Memory)
• Vercel Environment Variables Not Working (Undefined)
• Vercel Domain Not Verifying (Invalid Configuration)
• Vercel Unexpected Bill: Why Usage Charges Spiked
• Vercel Deployment Blocked: Commit Author Does Not Have Access
• Vercel Not Deploying After Git Push
• Vercel ERR_TOO_MANY_REDIRECTS With Cloudflare
• Vercel 413 FUNCTION_PAYLOAD_TOO_LARGE (4.5 MB Limit)
• Vercel Project Paused or Account Blocked