An asynchronous operation is one that does not wait for a response before continuing on. This allows operations to occur in a parallel. Thus, the operation does not, “block” or wait for the response.

Asynchronous operations will open a communication channel between the parties, make the request and close the channel before the response occurs. Message correlation is used to relate the inbound message to the outbound message. This method is effective when there are large numbers of transactions that could take long periods of time to process. In the case where the operations are short or need to run in serial, synchronous operations may be more appropriate.

Synchronicity is an issue in service design.