Performance degradation in Payload after upgrading Next.js

[TomSteer]

Describe the Bug

After upgrading Next.js in our project, the overall performance of Payload has significantly degraded (e.g., response times are much slower). Downgrading Next.js restores performance.
This issue can be reproduced using the Payload multi-tenant example by upgrading Next.js to the version mentioned below or newer.

Link to the code that reproduces this issue

https://github.com/payloadcms/payload/tree/main/examples/multi-tenant

Reproduction Steps

1. Clone the multi-tenant example from the Payload repo.
2. Upgrade Next.js from 15.2.3 → 15.5.4 (or newer).
3. Start the project and log in.
4. Interact with the admin panel and API endpoints.
5. Observe that response times and overall performance are significantly slower compared to the previous Next.js version.

Which area(s) are affected? (Select all that apply)

area: core

Environment Info

- payload: 3.59.1
- next: 15.5.4

[rilrom]

Have you narrowed down which specific version of next.js causes the slower responses? Is it 15.5.3?

[TomSteer]

No, I'll try and narrow it down.

[TomSteer]

The performance degradation starts in the 15.5 release.

[rilrom]

Looks like that version lines up with performance issues being reported in discord.

So far it seems the workaround is to keep Nextjs below that version or wait until Payload have resolved some Nextjs v16 issues and then upgrade.

[bratvanov]

The performance degradation starts in the 15.5 release.

I also noticed a dramatic slowdown of my project sometime during/after upgrading Next.js from <15.5 to >15.5. Since I had been updating other configs and dependencies around the same time, I wasn't sure if Next.js was the culprit, and thought I might have broken something somewhere else – but this report helps confirm my suspicions.

[AlessioGr]

I think this started somewhere between 15.4.2-canary.18 and 15.4.2-canary.5. Did not have time to narrow it down to the exact release yet

[AlessioGr]

Looks like this was introduced in 15.4.2-canary.17.

15.4.7 - fast:

15.4.7.mp4

15.4.2-canary.16 - fast:

canary.16.mp4

15.4.2-canary.17 - slower:

canary.17.mp4

16.0.2-canary.9 - slower:

latest.16.canary.mp4

It's not much slower, but I notice the difference.

Please let me know if these are the same performance issues you're experiencing. Can you test if 15.4.2-canary.17 is also the exact release that introduces these issues? Does it only happen in dev+turbo, or production as well?

[jakobpevec]

15.4.7 is the last fast version. I noticed that on projects with a lot of blocks performance degradation is severe in dev (turbo makes no difference). Load times can range from 15-30 seconds.

14.4.7:
✓ Starting...
✓ Ready in 767ms
○ Compiling /admin/[[...segments]] ...
✓ Compiled /admin/[[...segments]] in 2.8s
GET /admin 200 in 6664ms
-> subsequent page loads 1-4 seconds

15.5.*:
✓ Starting...
✓ Ready in 1590ms
○ Compiling /admin/[[...segments]] ...
✓ Compiled /admin/[[...segments]] in 3.3s
GET /admin 200 in 46091ms <- 46 second initial load
-> subsequent page loads 15-30 seconds

[jakobpevec]

@AlessioGr i've tested the canary versions, 15.4.2-canary.17 is the problematic one as you've also noticed. It happens in dev only, with or without turbo.

As I wrote in previous comment, on projects with lots of blocks it becomes unusably slow (load time in tens of seconds). If you need a reproduction repo let me know.