Non-blocking I/O and how Node uses it, in friendly terms: blocking vs async IO, CPU vs IO

An explanation of blocking versus non-blocking asynchronous I/O and how Node.js handles CPU and I/O tasks.

The work of fulfilling a request can be split into two pieces: CPU work, which is actively running code and performing calculations, and I/O work, which is waiting for something else to happen. Normally, threads performing I/O must wait until the I/O is complete to continue processing, which is called blocking or synchronous I/O. Non-blocking or asynchronous I/O is an optimization available in some technologies (NodeJS, Java NIO, and others) that allows threads to move on to other work while the I/O is happening in the background. Feel free to ask questions in the comments below! 00:00 Intro 00:31 Servers & Threads 01:28 A Server Is Like A Restaurant 03:22 A Request Has CPU work (active time) and I/O work (inactive time) 04:27 Code Example 05:03 Nonblocking I/O Timing Diagram 05:29 Blocking I/O Timing Diagram 06:01 Why Isn't Nonblocking I/O More Common? 06:47 Downsides Of Nonblocking I/O 07:42 Recap