Complicated Concurrency

Understanding asyncio and threading interactions in Python

This is a medium-difficulty Python concurrency question that tests whether you understand how asyncio and concurrent.futures interact, and when their combination breaks down. It's the kind of question that surfaces in technical interviews at firms where Python backend systems handle mixed async/threaded workloads.

The question focuses on a common pattern: offloading blocking I/O (like file writes) to a thread pool so the event loop remains responsive. However, not all modifications to such code preserve this behavior. Candidates need to reason about which changes disrupt the contract between the async event loop and the executor, or introduce subtle race conditions and deadlocks.

• Event loop lifecycle and blocking operations
• Thread pool execution semantics
• Futures and their resolution in async contexts
• Common pitfalls when mixing sync and async code