Google Drive API: Getting subscriptionRateLimitExceeded despite implementing exponential backoff and delay strategies

Question

I'm working with the Google Drive API and I'm facing an issue with rate limiting when subscribing to file updates using drive.files.watch. Despite implementing an exponential backoff strategy with increasing delays, I am still receiving the subscriptionRateLimitExceeded error after processing a batch of files. This issue occurs even with long delays between requests.

Observations:

1. I implemented exponential backoff, starting with a delay of 1 second and doubling it after each failed attempt (with a max backoff of 64 seconds).
2. Despite this, I still receive the subscriptionRateLimitExceeded error after a few requests, especially when processing a batch of files.
3. I also tried reducing the delay after multiple errors, but this still doesn't prevent hitting the rate limit.

What I've tried:

1. Exponential backoff: I doubled the delay time after each failed request and set a maximum backoff of 64 seconds.
2. Gradual delay reduction: After hitting the rate limit, I attempted to reduce the delay time gradually (after accumulating a few errors).
3. Global pauses: After each batch of 50 file subscriptions, I added a global pause of 10 minutes to prevent hitting the rate limit.

Question: Any insights on how to better throttle or adapt to rate limits for bulk subscription updates?