http uses a request/response style of communication
For simplicity, this pattern is typically implemented in a purely synchronous fashion, as in web service calls over HTTP, which holds a connection open and waits until the response is delivered or the timeout period expires. However, request--response may also be implemented asynchronously, with a response being returned at some unknown later time. This is often referred to as ``sync over async'', or ``sync/async'', and is common in enterprise application integration (EAI) implementations where slow aggregations, time-intensive functions, or human workflow must be performed before a response can be constructed and delivered.
Request–response