[00:01] with a choice about CAP theorem, but the real decision is a lot simpler than you refresher. CAP theorem stands for consistency, availability, and partition tolerance. The classic framing is that a distributed system can only guarantee
[00:14] two of the three. But, in a distributed system, the network will eventually partition tolerance is not optional. This means that CAP theorem isn't asking you to pick two of three. It's actually just asking one simple question. When
[00:27] the network does fail, do you return possibly stale data, which would mean an error, which would mean choosing consistency? Let's look at an example. Say your user updates their profile in the United States, and the connection to
[00:40] your Europe server goes down before that update is replicated. Then, a user in Europe requests the profile. Well, you have two options. You can show them the old picture, or you can refuse to answer until the network heals. For a social
[00:52] app, you'd clearly show them the old picture. Stale data is fine. An error availability. For Ticketmaster, on the other hand, selling the last seat at a concert, you would return an error. You'd rather tell somebody try again
[01:04] than sell the same seat twice. That's consistency. And so, when an interviewer three letters altogether. Just answer this one question. Is stale data acceptable or not? For a full breakdown on CAP theorem, head over to
[01:17] hellointerview.com. Our link is in the bio.