The Depths of Windows I/O (Part 3) — I/O Completion Ports (IOCP) and the .NET Thread Pool: The Basement Under async/await (archived 2026-08-30)

Part 3 of a series that explains I/O Completion Ports (IOCP) with diagrams. Covers the design that unifies the completion queue with thread-count control, the concurrency value and LIFO thread release, and works through to the .NET thread pool and which thread an async/await continuation runs on. Archived version of https://comcomponent.com/en/blog/windows-iocp-dotnet-threadpool/, as published on 2026-08-30. The live article is maintained and may change after this date. First published 2026-07-29.