What is CAP theorem?

CAP Theorem Made Simple

Imagine a Party!

Imagine you’re throwing a big party with friends, and you have a giant cake that everyone wants to eat.

Consistency: The Cake is the Same for Everyone

Consistency means that everyone at the party sees the same cake. If you cut a slice and give it to someone, everyone else should see that same slice gone when they look at the cake. It’s like making sure everyone has the same information.

Availability: Everyone Gets Cake When They Want

Availability means that whenever someone asks for cake, they get it. Even if some people are busy or the cake is running low, everyone who wants cake can have some. It’s like making sure the party doesn’t stop, and everyone can keep eating.

Partition Tolerance: The Party Goes On, Even if Some Rooms Are Closed

Partition tolerance is like when you have a big party in different rooms, and sometimes the doors between the rooms close. Even if people can’t move freely between rooms, the party can still go on in each room separately. It’s like making sure the party doesn’t crash just because some people can’t talk to each other.

The Trade-offs

Now, here’s the tricky part: you can’t have all three of these things at once. You have to pick which ones are most important to you.

• If you prioritize Consistency and Partition Tolerance, it means everyone sees the same cake (Consistency), even if some parts of the party can’t talk to each other (Partition Tolerance). But sometimes, when there’s a problem, you might have to pause the party until everyone can see the same cake again (Availability might suffer).

• If you prioritize Availability and Partition Tolerance, it means the party keeps going strong, and everyone gets cake whenever they want (Availability), even if different parts of the party can’t talk to each other (Partition Tolerance). But sometimes, people might see different cakes or stale cake (Consistency might suffer).

Examples

• Consistency-Priority Systems: Like a bank’s ATM network. It’s critical that everyone sees the same balance when they check their account, even if some ATMs can’t communicate with each other at the moment.

• Availability-Priority Systems: Like social media platforms. It’s more important that everyone can post and see updates quickly, even if there’s a temporary glitch showing different posts to different people.

In a Nutshell

Understanding the CAP theorem helps design systems that work well even when things go wrong. It’s like making sure the party stays fun, the cake stays delicious, and everyone has a good time, no matter what!