Internal. Not part of the supported API (see API inventory). It may change in any release, including a patch.

Admission control for the durable write path: at most :record_max_concurrency callers may hold a connection and an open transaction at once, and the rest are told :overloaded rather than queued behind a pool checkout that will time out somewhere unhelpful.

Why a process and not a counter

:counters would be cheaper and is wrong here. A caller that is killed with :kill runs no after block and no on_exit, so its permit would never be returned and the loss would be permanent: after enough kills the gate would refuse everything for ever. A process can monitor its callers, so a permit comes back when the caller dies however it dies.

There is no clock in this module

A concurrency limit at this timescale must not be decided by comparing two wall-clock instants: the shared database clock steps backwards by hundreds of milliseconds on this hardware (open-findings.md X100), and a node clock is worse. So the gate counts and monitors; it never expires anything. The only time value here is the GenServer.call/3 timeout, which is OTP's own monotonic timer and not a comparison of two stamped instants, and a caller whose call times out is refused rather than admitted.