A synchronous operation is one that waits for a response before continuing on. This forces operations to occur in a serial order. It is often said that an operation, “blocks” or waits for a response.

Synchronous operations will open a communication channel between the parties, make the request and leave the channel open until the response occurs. This method is effective unless there are large numbers of channels being left open for long periods of time. In this case, asynchronous operations may be more appropriate.

Synchronicity is an issue in service design.