Next.js ^15.1.0 consuming high CPU

[hdodov]

Summary

Once we upgraded to Next 15.1.0, we started experiencing weird CPU usage peaks at times of low request counts:

The above is our CPU usage vs request count for the last 2 weeks. Here's one for the last 3 hours, captured just now:

As you can see, request counts stay fairly stable, while CPU usage explodes…

Edit: Here's another screenshot — traffic stays the same, yet CPU usage drops significantly:

This has probably happened because the servers stopped getting overwhelmed with requests, as the response times had become near-instant — from ~0.80s to ~0.03s. Such response times only happen for cached content. Therefore, I think that something's wrong with the cache.

Does anyone experience something similar?

Related discussion: #73908

Additional information

Operating System:
  Platform: darwin
  Arch: x64
  Version: Darwin Kernel Version 23.6.0: Fri Nov 15 15:13:28 PST 2024; root:xnu-10063.141.1.702.7~1/RELEASE_X86_64
  Available memory (MB): 32768
  Available CPU cores: 16
Binaries:
  Node: 20.17.0
  npm: 10.8.2
  Yarn: N/A
  pnpm: 9.15.0
Relevant Packages:
  next: 15.1.1 // Latest available version is detected (15.1.1).
  eslint-config-next: 15.1.1
  react: 19.0.0
  react-dom: 19.0.0
  typescript: 5.7.2
Next.js Config:
  output: standalone

Example

No response

[hdodov]

@leerob do you think that the v15.1.0 release could contain some regression?

We heavily rely on the ISR cache to reduce server load, so my guess is that an increase in CPU usage could be due to some issue regarding the cache. This makes me suspicious of the following PRs that are part of the 15.1.0 release:

• [Segment Cache] Implement behavior on cache miss  #72841
• [Segment Cache] Interception routes #73434
• [Segment Cache] Use LRU to manage cache data  #73486
• [Segment Cache] Add isHeadPartial #73530

@acdlite @ijjk since you collaborated on those PRs, can you think of a reason why this happens?

@reh2ur has also noticed a similar issue since his upgrade to 15.1.0, as he has said here: #73908 (comment)