System Design
Intermediate
Free
Concurrency vs Parallelism
Threads, processes, and the event loop — what actually runs at the same time
14 min read
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Untangle four words engineers constantly confuse: concurrency, parallelism, threads, and processes. Learn what runs truly simultaneously versus what merely interleaves, why Python's async model is single-threaded, and how getting this wrong causes real production bugs like sharing one database session across coroutines.