How to do fine-grained caching: bulk APIs?

We're trying to turbo-charge our builds via fine-grained caching with the Pants build system. Pants recently gained experimental support for using the GitHub Actions Cache as a fine-grained "remote cache", to see the benefits discussed in https://dev.to/benjyw/better-cicd-caching-with-new-gen-build-systems-3aem, where we can reuse test runs and build artefacts from previous runs, while only downloading exactly what's required.

However, we find it doesn't work well in practice for us, even on a moderate sized repository, because doing fine-grained caching quickly hits rate limits (having to upload and/or download thousands of small "files" via individual requests). https://github.com/pantsbuild/pants/issues/20133

Are there any bulk APIs or other recommendations for how to best do the following:

1. Check whether several cache entries exist
2. Upload several new cache entries
3. Download several cache entries

Alternatively, some other way to use the cache for many small requests.

This might benefit more than just Pants, e.g. https://github.com/mozilla/sccache also has a GHA cache backend, but hits some errors like this (https://github.com/mozilla/sccache/issues/1485).

(I asked this question of support (#2409822), and they told me to ask here instead, even though it's not directly related to the code in this repo.)

Thanks!

No repository files or tests are named. Start by reviewing the GitHub Actions Cache API documentation and the linked Pants issue to determine whether bulk existence checks, uploads, or downloads are supported; done would require a maintainer-approved API answer or a clearly scoped implementation path.