Interviews

You have 47 browser tabs open. One is a YouTube video on consistent hashing. Another is a blog post about CAP theorem. Somewhere in the mix is a Reddit thread titled “How I cracked system design interviews in 3 months.” You have been studying for two weeks and somehow feel like you know less than when you started. The problem is not a lack of resources. It is the lack of a sequence. System design topics build on each other, and jumping straight to “design Twitter” without understanding database sharding is like trying to build a roof before laying the foundation. ...

You’re in a system design interview. You say “we’ll use PostgreSQL” and immediately follow it with “and we’ll shard it across 16 nodes.” The interviewer asks: “How much traffic are you expecting?” You don’t have a number. You just sharded because it sounded like the senior thing to do. Here’s the thing - most teams shard too early. A single PostgreSQL node can handle far more than people think. The decision to shard should come from actual numbers, not vibes. This post gives you those numbers. ...

You’re building a notification bell. The product team wants it to feel “real-time.” You reach for WebSockets because that’s what every blog post tells you. Six months later, you’re debugging a connection manager that handles reconnections, heartbeats, load balancer stickiness, and auth token refresh - all for a feature where a 5-second delay would have been perfectly fine. The problem isn’t picking the wrong tool. It’s not understanding the tradeoffs before picking. ...

Most candidates jump to drawing boxes on a whiteboard. Here’s the exact structure, order, and time allocation that turns a chaotic 45 minutes into a clear, compelling system design walkthrough.

Most candidates either skip estimation entirely or spend five minutes doing exact math. Here’s how to do quick, high-signal capacity estimation that actually drives architecture.

Saying ’the system should be scalable and highly available’ is not an NFR. Here’s how senior engineers define NFRs that actually drive architecture - with a framework, examples, and checklist.

Most candidates list features. Senior engineers define the system’s contract. Here’s a framework to get FRs right - with examples, anti-patterns, and a checklist.

Your college name is not the blocker you think it is. Here is a honest roadmap from someone who has seen both sides of the interview table.

You can solve hard LeetCode problems and still bomb interviews. The game has shifted, and most engineers have not noticed.