> IIRC GitLab uses Redis as well

GitLab employee here.

You're correct. We also have Redis for a few things: Rails caching, Sidekiq jobs, session data, CI, and a few other things. You can learn more about GitLab.com's infrastructure architecture here [1] and more about what Redis is used for here [2].

[1]: https://about.gitlab.com/handbook/engineering/infrastructure... [2]: https://docs.gitlab.com/ee/development/redis.html