I ended up using a ring buffer in Redis recently to store the last N values of some database lookups that are slow. It works great! Didn't take that much logic, either, since Redis has easy transactions. I just have the "current buffer index 'i'" as a key-value, the "buffer length 'N'" as a key-value, then 'N' numbered entries as key-values. I prefix these with the data identifier that it caches, so you can have several ring buffers active. you can do this with a Postgres table just as easily, I assume!

I also am building a ring buffer data structure for my hobby database that I use for personal stuff that uses FoundationDB [though I have been unhappy with the state of the FDB Go bindings, which are somewhat out of date versus the C client library for FDB and aren't very Go-like in design (the C libraries are the "gold standard" and they use FFI in all the other bindings to connect to those)].

Added later: it was a bit harder to deal with resizing the buffer, so when that happens I do some data shifing/dropping depending on which way we're resizing, effectively initializing the buffer anew because that was easier (again, a Redis transaction saves me a lot of concurrency work!), but lucky for me we would only resize each buffer at most 1 time per minute due to how our configs work.