The try-with-resource block is used to delineate an atomic transaction, and is part of the SpaceBase API. An example in the code for a blocking call is the call to receive.

Quasar identifies blocking methods if they declare that the throw a SuspendExecution exception, marked with a @Suspendable annotation, or listed in an external file. Pulsar, Quasar's Clojure API, marks suspendable functions differently, but that's an implementation detail.