Posts about system design
System breakdown: why a refund takes days when the payment took seconds
You cancel an order and the app says the refund has started. Your bank shows nothing for days. Here is where the money is in between, and which parts of the delay a shop can and cannot change.
System breakdown: why the 'order placed' screen sometimes lies
The app says your order is placed. Four minutes later it says one item is gone. Here is what the first screen really means, and how a well-built system keeps that promise honest.
System breakdown: how a flash sale doesn't melt the database
At 6 pm, 500 bags of rice go on sale at half price and thousands of people press Buy in the same few seconds. Here is how the system sells exactly 500, stays up for everyone else, and says no fast.
Find your system's limit before your users do
A design that works at today's traffic tells you little about next month's. In 15 minutes in the System Design Studio, you can find where a design breaks, what breaks first, and what one more user costs.
System breakdown: the rider dot that moves across your map
A delivery app shows the rider moving toward your door every few seconds. Here is the path one location update takes, and the three choices that keep it cheap.
System breakdown: what stops a double charge when you tap Pay twice
The network drops just after you press Pay with your mobile wallet. You press again. Here is how a well-built checkout makes sure you pay once.