How are HTTP responses matched?

Question

API

Greetings! Based on what exactly is the matching of http requests and http responses to them? Case - the client terminal sends several http requests to different APIs at the same time. How does he figure out which response came to which request? By the content of some header? Or deeper - at the transport level? But if on the transport - why exactly does he match?

Answer 1

In HTTP, everything is simple, one request - one connection - one response. You don't need to match anything.
If HTTP pipelining is used, then the responses must be returned strictly in the same sequence in which the requests were sent.