[00:01] embarrassing proportion of the time. How do you handle Black Friday or the end of the auction or the Super Bowl? Some events are predictable. You can definitely anticipate Black Friday and scale up your system in advance. But
[00:15] some are less so, like a link going viral or a celebrity post might mean you're scrambling for capacity. Many candidates I interview will reach for auto scaling. And this is kind of a solution, but spinning up a box takes
[00:29] minutes and scaling a database often means downtime or degraded performance during the spike. This is exactly when you can't afford it. So, you've got two real options, buffer or drop. Buffering in a system design setting usually means
[00:43] in a system design setting usually means a right queue. This is like Kafka or SQS between the app and the database. The app drops the right on the queue and responds instantly. Workers drain it at a sustainable pace.
[00:56] This is often times a good solution, but you need to know it's now async and it's only a temporary fix. If rights continue to come in faster than the workers drain, the queue grows forever and your burst turns into a full-blown outage.
[01:11] Dropping is often called load shedding. This sounds stupid, but it's actually really smart. We can throw away the least valuable rights. Uber drivers are reporting their location every few seconds. If we miss
[01:24] one update, we've only lost a little bit of accuracy. But we never want to drop a post that gets created. So, you've got a burst or a high-stress moment in your interview, buffer the bursts, shed the junk, and protect what
[01:38] matters. This is part three of four of our scaling rights series. Follow for breakdown on our website, hellointerview.com.