Node.js Request Lifecycle Explained: From Browser Click to Database and Back

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A three-part educational series on Node.js internals concludes with a walkthrough of the complete HTTP request lifecycle, from browser to database and back. The guide traces a login request through each layer: the operating system's network stack, libuv's event-driven socket notification, Node's HTTP parser, and Express middleware. It explains how libuv uses OS mechanisms like epoll to avoid blocking the CPU while waiting for socket data, and how Express middleware functions as a sequential chain of checkpoints each passing control via next(). The series aims to help developers understand Node.js deeply enough to explain the full request flow confidently in technical interviews.

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