In this case, that's correct—you could lose up to 5s worth of state, plus any buffered messages. That's by design here. The business impact of that is going to

In this case, that's correct—you could lose up to 5s worth of state, plus any buffered messages. That's by design here. The business impact of that is going to depend on use-case, but I personally would find it difficult to believe that there would be any real impact in that event, in this case, under high load. Obviously, different tolerances to that are going to necessitate different designs. You can configure the size of the message buffer when a GenServer starts, and if you have very low tolerance for lost data, you'd want to use a synchronous message (using call instead of cast, which blocks the sender until it returns) and appropriate error handling. BEAM has a plethora of features for reliable applications, you just have to apply them appropriately.