ELI5: what are denormalized reads

What is a denormalized read?

A denormalized read is when a database keeps extra copies of information stored together so you can find it faster, like keeping a phone number written in both your contacts AND your calendar instead of looking it up each time [3][5]. It's like having your favorite snack in every room of your house instead of just the kitchen [2].

Why do databases do this?

Normal databases organize information to avoid repeating data, but this means you have to search multiple places to get everything you need [3]. Denormalization puts related information together so your computer can grab it all at once without searching around [5].

What's the downside?

The problem is that if you need to change information, you have to update it in multiple places instead of just one [2]. This makes writing and updating information slower, even though reading it is faster [2].

When should you use it?

Denormalization works best when you're reading information way more often than you're changing it, like a news website where people read articles constantly but new articles are posted rarely [1][4].