I see you replied on comment below with:

> note that there are only one consumer and one producer

That clarify things as you don't need multi-thread coordination on reads or writes if assuming single producer and single consumer.

Thanks! That's not ensured, optimizations are only valid due to the constraints

- One single producer thread

- One single consumer thread

- Fixed buffer capacity

So to answer

> Are they ensuring two threads can't push to the same slot nor pop the same value from the ring?

No need for this usecase :)

This is a SPSC queue -- there aren't multiple writers to coordinate, nor readers. It simplifies the design.