> ## Documentation Index > Fetch the complete documentation index at: https://interview.anantapoudel.com/llms.txt > Use this file to discover all available pages before exploring further. # Introduction A complete, structured guide for mastering Node.js at an intermediate and senior level.\ This documentation is divided into five main pillars, each containing detailed technical topics, best practices, and interview-grade explanations. *** ## 1. JavaScript Foundations & Node.js Internals This section builds the core understanding required to program effectively in Node.js. ### Core JavaScript Topics * Scope, closures, hoisting * Promises and async/await * Event loop, microtasks, macrotasks * `this` binding and arrow functions * Destructuring, rest/spread * Array and object manipulation * Higher-order functions * ES6+ features (modules, classes, generators) * Error handling in async environments ### Node.js Runtime * V8 engine internals * Libuv event loop phases * Call stack, callback queue, microtask queue * Thread pool and non-blocking I/O * Worker Threads API * Process lifecycle * Environment variables * Global objects and timers * Differences between browser and server JavaScript ### Modules & Packages * CommonJS (`require`, `module.exports`) * ES Modules (`import`, `export`) * Core modules (`fs`, `path`, `os`, `crypto`, `http`) * npm/yarn package management * Semantic versioning * Module resolution and caching * Writing CLI tools and npm packages *** ## 2. Async Architecture, Streams, Events & Networking Master Node.js’ asynchronous nature and I/O systems. ### Asynchronous Programming * Callbacks and callback hell * Promises and chaining * Async/await best practices * `Promise.all`, `Promise.race`, `Promise.any` * Non-blocking I/O * Race conditions and synchronization * Error handling in async workflows ### File System & Streams * Reading/writing files (sync/async) * Directories and permissions * `Readable`, `Writable`, `Duplex`, `Transform` streams * Piping and backpressure * Compression (`zlib`) * Large file handling * File watchers ### Events & EventEmitter * Creating and listening to custom events * Removing listeners * Error events * Modular event-based architecture ### HTTP, HTTPS & Networking * Creating HTTP/HTTPS servers * Working with URL, query params * CORS handling * SSL/TLS configuration * WebSockets (`ws`, `socket.io`) * Reverse proxying with Nginx * Clustering and load balancing *** ## 3. Express.js, API Development & Validation This section focuses on building production-ready APIs using Express.js. ### Express.js Fundamentals * Creating apps and routers * Middleware lifecycle * Serving static files * Error handling middleware * Express 5 improvements * Environment-based configuration ### Routing & Middleware * `app.use`, `app.get`, `app.post`, `app.put`, `app.delete` * Modular routing * Route prefixes * Chaining middlewares * Third-party middleware (`cors`, `helmet`, `morgan`) * Global vs scoped middleware ### Request Handling & Validation * Parsing body, params, and query * Input validation using `express-validator`, `Joi` * Sanitizing inputs * File uploads with `multer` * Multipart form handling * Rate limiting and throttling ### Authentication & Authorization * Sessions and cookies * JWT authentication * Refresh token strategy * OAuth2 and OpenID Connect * Passport.js strategies * Role-based and policy-based access * CSRF and CORS security * Password hashing (`bcrypt`, `argon2`) *** ## 4. Databases, Caching, Queues & Performance Modern backend systems depend on databases, caching layers, and performance techniques. ### Database Integration * MongoDB with Mongoose * PostgreSQL, MySQL using query clients * SQLite for testing * Connection pooling * Transactions and ACID * Database indexing and query optimization ### ORMs & Query Builders * Prisma ORM * Sequelize * TypeORM * Knex.js * Handling relationships * Lazy vs eager loading * Migrations and seeding ### Caching & Queues * In-memory cache * Redis distributed caching * TTL strategies * Rate limiting with Redis * Queues with BullMQ, RabbitMQ, Kafka * Background processing * Pub/Sub architecture ### Performance Optimization * Cluster mode * Worker threads * Streams vs buffering * Load balancing * Database connection pooling * CPU/memory profiling * PM2 for multi-process management * Lazy loading modules * Monitoring GC and event loop delays *** ## 5. Microservices, DevOps, Deployment & System Design Advanced topics required to build scalable Node.js systems in real-world production environments. ### Microservices & Distributed Systems * Designing microservices with Express/Fastify * Communication via HTTP, gRPC, or message queues * API Gateway pattern * Event-driven architecture * Circuit breaker and retry patterns * Service discovery * Saga pattern for distributed transactions ### Background Jobs & Scheduling * Cron jobs (`node-cron`) * BullMQ delayed, retry, backoff jobs * Scheduled notifications * Queue-based processing workflows * Cleaning stale data ### DevOps & Deployment * Environment configuration (`dotenv`, `config`) * Docker and multi-stage builds * CI/CD pipelines (GitHub Actions, CircleCI) * Deployments on AWS, GCP, Azure * PM2/systemd for production * Reverse proxy with Nginx * Zero-downtime deployments ### Monitoring & Observability * Application metrics * Uptime and health checks * Logging aggregation (ELK stack, Graylog) * Distributed tracing (Jaeger, OpenTelemetry) * Alerts and dashboards (Prometheus, Grafana) * API analytics and audit logs ### System Design Concepts * Designing scalable REST APIs * Stateless and idempotent services * Real-time architecture via WebSockets * Caching layers and CDNs * Database sharding and partitioning * Multi-tenant architecture * Fault tolerance and graceful degradation *** # Start Learning Choose a topic below to begin your Node.js learning journey. Learn Node.js internals, runtime architecture, and advanced JavaScript. Understand streams, events, networking, and the event-driven model. Build production-ready APIs with routing, middleware, and security. Master databases, ORMs, caching, queues, and performance optimization. Learn microservices, DevOps, deployment, and distributed architecture.