Take a look at Maintner, a tool made by the Go team to load and store GitHub metadata, particularly issues, comments, reviews, and events: https://godoc.org/golang.org/x/build/maintner. It handles backoff, holds all data in memory, and supports backing up data to GCS.

My team is successfully using it to track ~200k issues/PRs across ~300 repos. We wrapped our deployment in a minimal API to give our infra blazing fast access to that data without needing to worry about GitHub auth or rate limits (since Maintner handles that).

And, we use the proxy described in the article.