Glossary term
What is I/O (Input/Output)?
I/O stands for Input/Output.
Reading/writing disks, network, files. Example: Waiting for a database reply is I/O.
Learn it properly · System DesignLesson 4: Processes, Threads & Concurrency for Backend EngineersMost backend work is waiting. How one server juggles thousands of requests — processes, threads, event loops and lightweight threads — and the race conditions, deadlocks and pool limits that appear the moment it does.