Study the event loop (phases, microtasks vs macrotasks), async programming (Promises, async/await, Promise.all), Express (middleware, error handling), MongoDB (indexes, populate, aggregation), security (JWT, bcrypt, NoSQL injection), performance (clustering, streams, worker threads), and deployment (PM2, Nginx, Docker, CI/CD). Practice coding questions.
Event loop (phases, microtasks, single-thread), modules (require/import, caching, circular deps), async programming (callbacks, Promises, async/await), Express (middleware, error handling, Router), MongoDB/Mongoose (schemas, indexes, populate, aggregation), security (JWT, bcrypt, injection, headers), and performance (clustering, streams, worker threads, memory, query optimization).
The event loop how it works, its phases (timers, poll, check, close), the difference between setTimeout/setImmediate/process.nextTick, and why Node.js is single-threaded. Understanding the event loop is essential for any Node.js developer.
Execution order: process.nextTick (after current operation, before next phase), Promise.then (microtask, after nextTick), setTimeout (timers phase), setImmediate (check phase, after I/O). nextTick and Promise are microtasks that run between phases; setTimeout and setImmediate are macrotasks that run in specific phases.
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