Node.js

High-level overview of how Node.js is structured and its core components.

V8 Engine

How Google's V8 Engine compiles and executes JavaScript inside Node.js.

libuv

The C library that powers Node.js asynchronous I/O and event loop.

Event Loop (Node.js)

The phases of the Node.js event loop and how callbacks are executed.

Worker Thread Pool

How libuv uses a pool of background threads to prevent blocking the event loop.

2. Async Programming

Callbacks

The foundational pattern for handling asynchronous operations in Node.js.

Async / Await

Modern, synchronous-looking syntax for handling Promises in Node.js.

process.nextTick

A mechanism to defer the execution of a function until the current operation completes, before the Event Loop continues.

setImmediate

How to schedule a callback to run on the next iteration of the event loop.

3. Events

Event Emitters

How the Observer pattern is implemented in Node.js via the EventEmitter class.

4. Streams

Streams Overview

Handling large amounts of continuous data efficiently in Node.js.

Backpressure

How Node.js streams handle speed mismatches between reading and writing.

Readable Streams

Working with streams that act as a source of data.

Writable Streams

Working with streams that act as a destination for data.

Transform Streams

Duplex streams where the output is computed from the input.

5. Modules

CommonJS vs ESM

The two module systems used in Node.js and their key differences.

Module Resolution

How Node.js locates and loads modules when you call require() or import.

Module Caching

How Node.js caches required modules to improve performance and share state.

6. Networking

HTTP Module

The core module for building HTTP servers and clients in Node.js.

HTTPS & TLS

Securing network communication in Node.js using HTTPS and TLS/SSL.

HTTP Keep-Alive

Reusing TCP connections to improve network performance.

WebSockets

Persistent, bidirectional, full-duplex communication over a single TCP connection.

AbortController

How to cancel ongoing asynchronous operations like network requests.

7. Concurrency

Worker Threads

Executing CPU-intensive JavaScript operations in parallel.

Child Processes

Executing system commands and spawning external programs from Node.js.

Cluster

Scaling Node.js web servers across multiple CPU cores.

Worker Pools

Managing a pool of worker threads efficiently to avoid startup overhead.

8. Memory

Memory Management

How memory is allocated and structured in Node.js (V8).

Garbage Collection

How V8 reclaims memory using the generational garbage collector.

Memory Leaks

Common causes of memory leaks in Node.js and how they occur.

9. Performance

Profiling

Techniques and tools for identifying performance bottlenecks in Node.js.

Event Loop Lag

Understanding and measuring the delay caused by blocking the event loop.

Optimization

Techniques for optimizing Node.js applications for speed and scale.

10. Errors

Error Handling

Best practices for handling operational and programmer errors in Node.js.

uncaughtException

How to handle synchronous errors that bypass your try/catch blocks.

unhandledRejection

How to handle Promises that reject without a .catch() block.

11. Lifecycle

Graceful Shutdown

How to safely stop a Node.js server without dropping active connections.

12. Security

CORS

Understanding Cross-Origin Resource Sharing and how to configure it in Node.js.

Prototype Pollution

A dangerous vulnerability unique to JavaScript where attackers overwrite prototype properties.

SSRF (Server-Side Request Forgery)

A vulnerability where an attacker forces the server to make unintended HTTP requests.

Dependency Security

Managing the risks associated with third-party NPM packages.

13. NPM

package.json & lockfiles

Understanding how Node.js manages project dependencies and versions.

2 min read

Dependency Management

How to effectively manage updates and security for NPM packages.

npm ci vs npm install

Why you should never use npm install in your CI/CD pipelines.

2 min read

14. Testing

Unit Testing

Testing individual functions and classes in isolation.

Integration Testing

Testing how different parts of your application work together.

Mocking & Stubbing

Faking dependencies in tests to isolate the code being tested.

15. Debugging

Node Debugger

Using the built-in V8 inspector to debug Node.js applications.

Heap Snapshots

Capturing and analyzing the V8 memory heap to find memory leaks.

CPU Profiling

Identifying slow synchronous code blocking the event loop.

16. Observability

Logging

Best practices for structured logging in Node.js backend applications.

Metrics

Instrumenting Node.js to track continuous numerical data like CPU, memory, and request rates.

Distributed Tracing

Following a request's journey across multiple microservices.

17. Backend Concepts

Middleware

The pattern of using functions to intercept and modify HTTP requests in Express.

Connection Pooling

Reusing database connections to handle high concurrency.

Caching

Improving performance by temporarily storing frequently accessed data.

Rate Limiting

Protecting your API from abuse by limiting the number of requests a user can make.

Retries & Exponential Backoff

Building resilient microservices by safely retrying failed network requests.

Idempotency

Ensuring an operation yields the same result no matter how many times it is executed.

18. Advanced

Node.js C++ Addons

Extending Node.js by writing native C++ modules.

WebAssembly (WASM)

Running compiled native code securely and efficiently inside Node.js.

Buffers

Handling raw binary data directly in Node.js.

19. Interview

System Design with Node.js

How to architect and scale Node.js applications in a system design interview.

Coding Patterns

Common design patterns expected in Node.js coding interviews.