My understanding is that all client/server models are either Iterative or Concurrent, and concurrency can be implemented using a combination of multi-processing, multi-threading, and/or asynchronous I/O like select or poll. Is that correct? I'm a bit lost with the lecture notes, particularly pg.9 in lecture 9 labels multiple processes per client as an iterative server but I thought this would be a concurrent server setup? Question 4b in the 2023 exam asks for 3 distinct models of server process construction. I'm a bit stuck on the meaning of process here, but would it be correct to say that the models would be single process single thread (iterative), single process with many threads (concurrent), and many processes (concurrent)? Thanks for your help.

single thread, multi thread, event driven

I went towards the client/server direction. Do two-tier, three-tier and n-tier architectures also work?