How to create/call Asynchronous web service in a flow service?

For Example:

There are 5 steps in flow service.
-->First Step is Invoke web service, that inserts the data into database and it takes 10 min to complete.
-->Remaining 4 steps should not wait until the completion of web service.
-->Without waiting for reply, next flow steps should complete the execution at client side and that process should run at server side.
Please share ur suggestions..

Simple. Create a service A which has a publishable document type that is subscribed by another service B that hosts the webservice. Rest you put in the master service.

You would be able to run the service as a normal service and the 10min part will be handled by the broker.

Thank you.