sentry-cli: Slow sourcemap upload

I’m having issues with the upload time to sentry.io.

Our sourcemaps are ~30mb, and it takes over 5 minutes to upload them. As we do this as part of CI it slows our build times down.

Unlike https://github.com/getsentry/sentry-cli/issues/17 the upload is consistently slow.

The upload is happening from our corporate network (very fast internet), so it seems unlikely it is related to our connection. (e.g. uploading the same sourcemaps to other cloud providers takes just seconds)

Our build script calls this (after first verifying if a release exists, and creating one if not):

sentry-cli releases -p OUR_PROJECT files OUR_REVISION upload-sourcemaps ./path/to/built/code

There is a ~/.sentryclirc which specifies some defaults (our org, auth token, log level etc)

Can anyone suggest ways to speed this up / further investigate why it’s slow?

I’ve run the upload with log level trace but didn’t see anything illuminating in the log.

EDIT: one thing I just noticed is for some files it first requests a DELETE for that file before doing the POST. I’m not sure why it would do this as I’m creating a new release each time before uploading, so there should be no existing files associated with the release.