Threw together this very specific proxy that allows the downstream to define which IP will be used for the proxied request, and has built-in rate limiting mechanism to coordinate upstream rate limiting across clients.

This is particularly useful when you have a proxy node with many IPs, and you either want to use a specific one, or rotate through them. It also helps prevent upstream rate limiting due to disjoint clients being unable to coordinate on rate limits.

Opus was largely able to one-shot each feature from my specs, which was pretty cool (shows how effective a spec is).