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Node.js

Server-side JavaScript with Node.js — the event loop and concurrency model, modules and npm, async patterns, streams, error handling, building APIs with Express, databases and ORMs, testing, and security and scaling.

Questions

Topics

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Topics

Choose a topic to start your interview preparation journey

Node.js Fundamentals & Architecture

How Node.js works under the hood — V8, libuv, the single-threaded non-blocking model, the process/global objects, and how it differs from the browser.

5 Qs~13 min

Modules & npm

How Node loads code — CommonJS vs ES Modules, require resolution and caching, package.json and semantic versioning, dependency types and lockfiles, and npm/npx tooling.

5 Qs~14 min

Event Loop & Concurrency

The heart of Node's performance — the event loop phases, microtasks vs macrotasks, process.nextTick vs setImmediate, keeping the loop unblocked, and scaling CPU work with worker threads, cluster, and child processes.

5 Qs~15 min

Asynchronous Patterns

Writing correct asynchronous code — callbacks and the error-first convention, Promises and their combinators, async/await and promisify, the EventEmitter pattern, and running work in parallel vs sequence.

5 Qs~15 min

Streams & Buffers

Processing data efficiently — the four stream types, backpressure and piping, Buffers for binary data, flowing vs paused mode, and why streaming beats loading everything into memory.

5 Qs~14 min

Error Handling

Building robust services — handling errors across callbacks/promises/async-await, uncaughtException and unhandledRejection, operational vs programmer errors, custom error classes, and graceful shutdown.

5 Qs~15 min

Building APIs with Express

Building HTTP services — the http module vs Express, middleware and its execution order, routing and route parameters, error-handling middleware, and REST API design conventions.

5 Qs~15 min

Security, Performance & Scaling

Running Node in production — common vulnerabilities and mitigations, password hashing and authentication, caching, scaling across cores and machines, and finding performance bottlenecks.

5 Qs~15 min

Databases & ORMs

Persisting data from Node — choosing SQL vs NoSQL, ORMs and query builders (Prisma, Sequelize, TypeORM, Mongoose), connection pooling, transactions, and avoiding injection and N+1 queries.

6 Qs~18 min

Testing

Verifying Node applications — the testing pyramid, Jest/Mocha, mocking and test doubles, integration-testing Express APIs with supertest, testing async code, and coverage/TDD practices.

6 Qs~18 min