Why is request/response not a fit for an event driven service in your view? A lot of request/response server apps are written using the event model.
The two styles are an impedance mismatch.
Also request/response is not inherently synchronous or asynchronous. It's just a protocol design pattern.
Buffering, overcommit, etc are also kust normal facts of life in both sync and async messaging.
Request/response is fundamentally synchronous. If you want to nitpick about other layers not blocking, that’s missing the wood for the trees.
Each Lambda invocation gets a dedicated VM for the duration of the request. It is a great match for synchronous code.
Lambda does reuse VMs, so I hope you aren’t relying on containers being discarded for any integrity or security outcomes.
All the responses in this thread illustrate to me that AWS needs to put more effort into socialising how the product works. Since I was physically in the room for Lambda’s AWS internal launch this is twice disappoint because the technical messaging then was very clear and compelling.