I am a little confused. Isn’t optimistic for performance and pessimistic for correctness? I thought when there is low data contention, a system might not rely on locks but rather checks to see if the data has been modified before committing the transaction, and therefore it would be considered optimistic. And then when you expect there to be more contention, or you are being pessimistic, you might choose to some sort of locking mechanism to ensure only one process has write access at a time. So it seems like everything about your answer makes sense if I swap the terms optimistic and pessimistic. Is there something I am not understanding? It seems that the handling of messages by a saga uses optimistic concurrency, but the creation of sagas uses pessimistic concurrency, since the uniqueness of a correlation ID is enforced. Is this fair to say?