Grokking Scalable Systems for Interviews

What it covers

Scaling as a sequence of decisions rather than a single property. Vertical before horizontal and when that stops working, why statelessness is the precondition for everything else, where caching helps and where it hides a design problem, read replicas, partitioning strategies, and the point at which the database stops being the answer.

The framing that helps

Systems do not become slow uniformly. They hit a specific bottleneck at each scale, and the useful skill is predicting which one comes next. A candidate who says "at ten times this load the write path becomes the constraint, so here is what I would change" is demonstrating exactly what the round measures.

How to use it

Practise the estimates. Rough capacity numbers, done out loud in ninety seconds, are a standard part of the round and one of the easiest parts to rehearse.

Best for: design candidates who can draw a system but freeze when asked what happens at ten times the traffic.