Scheduling Mechanisms In Node.js Execution.

Many developers think Node.js runs async code in the order it appears in the file. It doesn’t.

Execution order depends on synchronous code, process.nextTick(), microtask queue, and event loop phases.

When code runs, different types of work go into different queues. Like nextTick(), promise microtasks, and phase-based queues in the event loop.

First, Node.js runs all synchronous code. Things like console.log() or normal function calls. Only after that it starts dealing with queued work.

process.nextTick() runs first. It has higher priority because Node.js uses it for internal and critical callbacks that need to run right after sync code, before promises.