> It looks like these are more lower level libraries so clients are supposed to block, but they are responsible for doing the blocking themselves.

You busy spin when blocking (fastest) or you can use a WaitStrategy from https://www.github.com/coralblocks/CoralQueue. You can see an example here: https://github.com/coralblocks/CoralQueue/blob/main/src/main...

> And given these are designed for "ultra-low-latency" systems, I don't think that's a big problem because the best blocking strategy is probably just to spin.

If you have an isolated and dedicated CPU core for your thread, that's correct. Busy-spinning is the fastest/best strategy.

> It would be nice if the docs were nicer though, considering this is a paid product...

CoralRing and CoralQueue are open-source and free at GitHub. There are also a lot of documentation and explanations on the GitHub README.me page (front page). The code has also a lot of comments.