This document discusses different server architecture models for handling requests efficiently, including: 1) The fork-exec model is useful for long-running requests but inefficient for HTTP. 2) The pre-forking model uses a pool of processes/threads to listen, process requests, and wait for more work. 3) The Win32/WinNt model uses threads within two processes for efficiency. 4) The Linux/Unix model combines multiprocessing and multithreading by using processes with fixed threads each. 5) A thread pool model creates threads at startup to quickly service requests and return threads to the pool.