Node is a nonblocking Javascript runtime. You can concurrently run an HTTP Server, read files from disk, send UDP datagrams, accept TCP connections from clients and still have room to execute Javascript code operations without blocking. Most of these operations are known as I/O, you send an input to a device, file or a socket and it replies back with an output. Node achieves nonblocking I/O with mostly a single thread executed asynchronously using a library called lib_uv.
The exception being DNS queries, which use a thread pool. This means when you use fetch or axios to make an HTTP request to a domain, the DNS resolution for that domain will most probably go through the thread pool, while the actual request itself will be sent asynchronously on the main thread.

In this episode of the backend engineering show I go through an article I wrote discussing NodeJS Asynchronous I/O.

  / whennodejsioblocks  

Learn the fundamentals of network engineering, get my udemy course
https://network.husseinnasser.com'>https://network.husseinnasser.com

0:00 Intro
3:00 Part 1 Socket/IO
9:48 Part 2 File I/O
12:42 Part 3 DNS
16:22 Part 4 NodeJS Single Threaded
19:10 Part 5 NodeJS Thread Pool
21:23 Part 6 DNS lookup bottleneck in Node


Fundamentals of Networking for Effective Backends udemy course (link redirects to udemy with coupon)
https://network.husseinnasser.com'>https://network.husseinnasser.com

Fundamentals of Database Engineering udemy course (link redirects to udemy with coupon)
https://database.husseinnasser.com

Introduction to NGINX (link redirects to udemy with coupon)
https://nginx.husseinnasser.com

Python on the Backend (link redirects to udemy with coupon)
https://python.husseinnasser.com

Become a Member on YouTube
   / @hnasr  

Buy me a coffee if you liked this
https://www.buymeacoffee.com/hnasr

Arabic Software Engineering Channel
   / @husseinnasser  

Members Only Content
   • Membersonly videos  



Backend Engineering Videos in Order
https://backend.husseinnasser.com

Database Engineering Videos
   • Database Engineering  

Listen to the Backend Engineering Podcast
https://husseinnasser.com/podcast

Gears and tools used on the Channel (affiliates)

Slides and Thumbnail Design
Canva
https://partner.canva.com/c/2766475/6...


Stay Awesome,
Hussein