StorePool

The connections a store draws from, as its pool says them: a facet of a Store (Store.facet) whose pool can say them (HikariCP's, the MongoDB driver's, the Elasticsearch client's), so that the node bounds the store's queries by its pool and reads its write pressure from it. A store whose pool says nothing has none: its queries take the default bound and its write pressure is its append latency alone.

Every member reads what the pool already counts: it does no I/O, and the node calls waitingForConnection about once a second.