Adam here, the author of rlimit, great to see some discussion and pointers on what I need to work on when it comes to pitching the project.

rlimit is a distributed counter, keeping counters in sync in several regions, allowing you to have consistent rate limiting, everywhere.

If you run on a single machine, there are low to no benefits for you in using rlimit. If you use multiple machines (or serverless runtime), you will likely need something to sync counters - this can be Redis, or you could just sign up for rlimit, and have the counter replicated globally out of the box.