Apigee request processing

what is the request processing model within Apigee?

are sessions created for each incoming request ?

Details on the request processing model can be found here: https://docs.apigee.com/api-platform/fundamentals/what-are-flows?hl=en

Depending on what exactly you mean by “session”, yes - variables are not shared between requests unless done explicitly (eg, via KVM / cache / Developer App custom attributes)