FUNCTION_INVOCATION_TIMEOUT on Vercel
A Vercel Function ran longer than its allowed duration. The documented causes are slow upstream calls, no response, an infinite loop or an unhandled exception.
FUNCTION_INVOCATION_TIMEOUT (Gateway Timeout)What it means
Vercel documents this error as a function invocation that takes longer than the allowed execution time. The cause can be an error in the function, a slow network call, or the environment the function runs in.
How to fix it
- Make sure API and database requests made by the function answer within the maximum duration for your plan.
- If the work needs more time, Vercel suggests enabling Fluid compute for significantly longer durations. For work that needs unlimited execution time, it points to Vercel Workflows.
- Make sure the function always returns an HTTP response, even an error response. A function that returns nothing times out.
- Check that no loop runs forever.
- Check that any external API or database the function calls is not failing.
- Look for unhandled exceptions in the application logs, which are available at the deployment's host URL under the /_logs path.
What a DeployDoctor scan can check
A repository scan cannot measure how long a request takes, so it cannot confirm or diagnose a timeout. It can flag server code that Vercel cannot run at all, such as Playwright, Puppeteer, SQLite bindings and filesystem writes.
Sources
Documentation last checked 2026-10-28. Vercel can change its documentation; confirm against the linked pages.