Verify 900s maxDuration is actually honored for pages/api routes and your hosting plan.

Bumping to 900s is reasonable for large zips, but many platforms cap synchronous Serverless HTTP at lower limits (often 60–300s), or only allow 900s for background jobs. If unsupported, clients will still see timeouts/504s long before Lambda returns.

Run these to cross-check consistency and hosting constraints:

And confirm provider support/limits:

🏁 Script executed:

#!/bin/bash
# 1) Where else do we set maxDuration? Ensure consistency across API routes.
rg -n -A 2 -B 2 'maxDuration\s*:' --no-ignore

# 2) Check if any routes are set to edge runtime (AWS SDK won't work there).
rg -n -A 1 -B 1 'export const runtime\s*=' --no-ignore

Length of output: 4625

🌐 Web query:

For Next.js pages/api deployed on Vercel, does `export const config = { maxDuration }` apply, and is 900 seconds supported for synchronous Serverless Functions? If not, what are the supported max durations and the correct way to run up to 15-minute jobs?

💡 Result:

The export const config = { maxDuration } directive does apply to Next.js API routes (pages/api) deployed on Vercel, but the maximum value supported for synchronous Serverless Functions varies by plan and whether “fluid compute” is enabled. Running synchronous functions for 900 seconds (15 minutes) is generally only possible on Enterprise plans without fluid compute enabled, and is not supported for synchronous functions on most plans or configurations[1][8].

Key duration limits for Next.js API routes on Vercel:

• Fluid compute is enabled by default for most projects[1][8].
• With fluid compute enabled, Enterprise and Pro both max out at 800 seconds (13 minutes 20 seconds).
• Only Enterprise plans with fluid compute disabled can reach 900 seconds (15 minutes)[8][1].

How to set function duration:

• Set maxDuration in the API route file as part of the exported config:

  export const config = { maxDuration: 800 };

• Alternatively, configure maxDuration per-route or with glob patterns in your vercel.json[1].

Running synchronous jobs up to 15 minutes:

• Not supported for synchronous serverless functions unless you are on Enterprise, with fluid compute disabled. For all other scenarios, you are limited to 800 seconds, or less depending on plan/configuration[1][8].
• For background tasks longer than your duration limit, use asynchronous techniques: queue the job to a persistent background worker service (for example, using queues like AWS SQS, or third-party background services), and return an initial response to the client rather than blocking for completion[9].
• If you need to perform additional work after the response, investigate the use of waitUntil or Next.js's experimental after API in conjunction with fluid compute. This allows background processing, but is only suitable for non-blocking, fire-and-forget tasks and may still be duration-constrained[9].

Summary of best practices for long-running jobs:

• For jobs up to 13:20 minutes: use maxDuration: 800 and Pro/Enterprise plan with fluid compute[1][8].
• For jobs up to 15 minutes: Only use synchronous API routes on Enterprise plans with fluid compute explicitly disabled[8].
• For any jobs requiring reliable execution over 800 seconds, or if not on Enterprise, run the task asynchronously outside the Vercel serverless execution environment.

In conclusion:
900 seconds (15 minutes) is only supported for synchronous serverless functions on Enterprise plans with fluid compute disabled[8][1]. For most use cases on Vercel, the max achievable duration for synchronous serverless (API) routes is 800 seconds on Pro/Enterprise with fluid compute enabled. To run jobs up to 15 minutes or longer, delegate work to a background worker/service so that your API route can respond within platform-mandated limits.

References:
[1]: Vercel Docs – Maximum Duration Configuration
[8]: Vercel Docs – Vercel Functions Limits
[9]: Vercel Docs – Avoiding Timeout, Fluid Compute
[10]: Vercel Docs – Configuring Functions

Citations:

• 1: https://vercel.com/docs/functions/configuring-functions/duration
• 2: https://www.youtube.com/watch?v=YuzKlQxMVUI
• 3: https://community.vercel.com/t/build-warning-in-deployment-after-adding-vercel-json-file/507
• 4: maxDuration and server actions vercel/next.js#58855
• 5: https://vercel.com/changelog/serverless-functions-can-now-run-up-to-5-minutes
• 6: The maxDuration setting in the api route config, as per the documentation, isn't being honored on dev or on Vercel. We're on the pro plan. vercel/next.js#66462
• 7: https://vercel.com/docs/limits
• 8: https://vercel.com/docs/functions/limitations
• 9: https://vercel.com/guides/what-can-i-do-about-vercel-serverless-functions-timing-out
• 10: https://vercel.com/docs/functions/configuring-functions