When I worked with bounded Redis streams a couple of years ago we had to implement our own backpressure mechanism which was quite tricky to get right.

To implement backpressure without relying on out of band signals (distributed systems beware) you need to have a deep understanding of the entire redis streams architecture and how the the pending entries list, consumers groups, consumers etc. works and interacts to not lose data by overwriting yourself.

Unbounded would have been fine if we could spill to disk and periodically clean up the data, but this is redis.

Not sure if that has improved.

I don't have a direct comment to add, but after working on the fringes of streams a bit, they've worked as advertised, but the API surface area for them is full of cases where, as you say, you have to kind of internalize the full architecture to really understand what's going on. It can be a bit overwhelming.