We've all been there. You order a pint of ice cream on an ultra-fast delivery app like Flipkart Minutes. The app promises it'll arrive in 10 minutes.
But what if 10 minutes pass, your ice cream is stuck in traffic, and you want to cancel? The app should give you a "Cancel Order" button.
Now look at it from the driver's perspective. If they just arrived at your doorstep, you shouldn't be able to cancel the order at the last second and get free ice cream. The button must vanish the exact millisecond the driver arrives.
Handling this for one person is easy. But how do you build this when 60,000 people are ordering at the same time, flooding your system with 100,000+ requests every single second?
Let's dive in.
