Understanding the CAP Theorem

The Ultimate Guide to Selecting the Perfect Database for Your Needs

Confused about choosing the right database? Here’s everything you need to make the perfect choice for your project.

✨ Note: Non-members can read the full story here.

Imagine you’re at a bustling café, enjoying a sunny afternoon, and the barista is struggling to fulfil everyone’s coffee orders. The café has two baristas, and their job is to make sure everyone gets the exact order they asked for — whether it’s a latte, espresso, or a cappuccino — and at the same time, do it as quickly as possible. Now, let’s say one of the baristas decides to prepare coffee without checking what the other is doing, just to speed things up. Can you see the problem here? Some customers may end up with a drink they didn’t ask for. This situation is not very different from what happens in distributed systems — specifically when dealing with the CAP theorem.

The CAP theorem explains the trade-offs that are inevitable when building distributed systems that need to deal with data shared across multiple servers or nodes. It tells us that when designing such systems, we can only choose two out of the three properties: Consistency, Availability, and Partition Tolerance. To make it easier to understand, let’s take a deeper look at what these mean, using examples you might encounter in everyday life.