wso2:esb: What is the basic difference between call mediator and send mediator

Send mediator - used to send messages out of Synapse to some endpoint. Then the response is returned to the OutSequence where you can send it back to the client

Use cases - When you only need to send a message to one back end and return the response back to the client.

Call mediator - Also used to send messages out of the Synapse to some endpoint, but the response does not come to the OutSequence. When we send a request using the call mediator, the response will arrive to the mediator that is placed right after the call mediator.So this will allow us to specify all the service invocations one after the other in a chain within a single sequence

Use cases - Service chaining. i.e.- Vehicle license renewal service