Is REST synchronous or asynchronous interaction?

REST (Representational State Transfer) is an architectural style for building web services that does not impose strict constraints on whether interactions are synchronous or asynchronous. Typically, REST interactions are implemented over the HTTP protocol, which is synchronous: the client sends a request and waits for a response.

However, from an architectural perspective, REST can also be used in asynchronous scenarios, for example, when the client initiates a request, and the response arrives later through another channel (such as a webhook or polling).

Thus, REST is most often associated with synchronous interactions, but it does not exclude asynchronous patterns when implemented accordingly.