Here count is employed solely for counting purposes, rather than for synchronizing access to other shared variables. While Ordering::SeqCst guarantees program correctness, it can also impact performance. Therefore, using Ordering::Relaxed is sufficient to maintain the program's correctness without adversely affecting its efficiency.
https://github.com/blackbeam/rust-mysql-simple/blob/e0fbfe41f23e9004a0bd7f997c388591ce07b40b/src/conn/pool/inner.rs#L70-L84
Here
countis employed solely for counting purposes, rather than for synchronizing access to other shared variables. While Ordering::SeqCst guarantees program correctness, it can also impact performance. Therefore, using Ordering::Relaxed is sufficient to maintain the program's correctness without adversely affecting its efficiency.