500: INTERNAL_SERVER_ERROR / FUNCTION_INVOCATION_FAILED on Vercel

What it means in plain English

Your server code threw an error and crashed. The logs tell you exactly why; the page itself doesn't.

Likely causes

• A missing env var (code reads undefined).
• A package that only works locally or needs a different Node.js version.
• Database unreachable or out of connections.

How to fix it, step by step

1. Vercel → Project → Logs (runtime) → filter by the failing path → read the error message and stack trace.
2. If it mentions undefined or a missing key: add the env var for Production and redeploy.
3. If it's a Node version issue: set it in Project Settings or package.json "engines": { "node": "22.x" }.
4. If it's database connections, see the 'too many connections' page.
5. Paste the exact log error into Cursor/v0 and ask for a fix, rather than describing the symptom.

How to check it worked

• The route returns 200 and the logs are clean.

Sources

• https://vercel.com/docs/environment-variables (opens in a new tab)
• https://vercel.com/docs/functions/runtimes/node-js/node-js-versions (opens in a new tab)
• https://vercel.com/docs/functions/limitations (opens in a new tab)