Got no such file error when call api on vercel

[nameczz]

Summary

Running the code locally works fine, regardless of whether I use yarn dev or yarn start after build.
But when deploy on vercel successfully, open the site, when call /api/milvus/search will throw

An error occurred while writing the file to cache: [Error: ENOENT: no such file or directory, mkdir '/vercel'] {
  errno: -2,
  code: 'ENOENT',
  syscall: 'mkdir',
  path: '/vercel'
}

But the code does not use mkdir to create any folder at all.
Any idea? thanks!

Example

https://github.com/nameczz/milvus-node-demos/blob/master/semantic-image-search/src/app/api/milvus/search/route.ts

Steps to Reproduce

1. deploy on vercel
2. call search api
3. get error in vercel log