Concurrency & the event loop

Summary

Deep understanding of how Node.js handles concurrency despite being single-threaded — a frequent, somewhat tricky interview topic that trips up candidates who've only used async/await without understanding it.

• 1Practice explaining the event loop phases and the microtask/macrotask queue distinction.
• 2Be ready to predict the output order of a tricky async code snippet.
• 3Understand what actually blocks the event loop and what doesn't.