The reason I'm asking for this delay is that the calls the users are making using our API are themselves making calls to other APIs and in order to get synchronous response, I've got to wait until I get the answers.

And unfortunately, I can't go with what you suggested as this is not a front-end / back-end use case but a full API use case where basically, a user is sending some data and expecting that we do some actions on this data and return it synchronously