Design Uber / a Ride-Hailing System - System Design
“Design Uber” sounds like a CRUD app with a map on top. A rider taps a pin, a driver shows up, money moves. The interviewer lets you believe …
Read MoreDesign a URL Shortener (TinyURL) - System Design
Everyone thinks the URL shortener is a trivial problem. “It’s a hash map. Store long URL, return short URL, done.” Then the interviewer …
Read MoreDesign Twitter's News Feed - System Design
The Twitter timeline looks trivial until you say the numbers out loud. “Show me a list of tweets from people I follow, newest first.” It is …
Read MoreDesign WhatsApp / a Chat Messaging System - System Design
A chat app sounds like the easiest system you will ever build. “User A sends a message, user B receives it.” One INSERT, one SELECT. The …
Read MoreThe Real Cost of Running Production Systems
You just shipped a new service. It works. The demo went great. Leadership is happy. Then the bill arrives - not just the AWS invoice, but …
Read MorePostgreSQL Is All You Need (Until It Isn't)
You’re three months into a new project. You have a PostgreSQL database for your core data, Redis for caching, Elasticsearch for search, …
Read MoreSystem Design Roadmap - What to Learn in What Order
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 …
Read MoreHow to Integrate the ChatGPT API - A Complete Guide for Developers
You’ve used ChatGPT through the web interface. Now you want to build it into your own app - a customer support bot, a code review tool, a …
Read MoreHow Redis Went from Single-Threaded to 3.5 Million Ops/Sec
“Redis is single-threaded.” You’ve heard this in every system design interview, every blog post, every tech talk. It was true in 2009. It’s …
Read MoreRedis Internals - Clustering, Sentinel, Sharding, and Pipelining Explained
You spin up a single Redis instance, throw your session data in it, and everything works great. Then your app grows. One day Redis goes down …
Read MoreDatabase Ops/Sec and Memory Limits - When to Shard and When Not To
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 …
Read MorePolling vs Long Polling vs WebSockets - When to Use What
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 …
Read MoreHow to Structure a System Design Interview in 45 Minutes
Most candidates jump to drawing boxes on a whiteboard. Here’s the exact structure, order, and time allocation that turns a chaotic 45 …
Read MoreBack of Envelope Calculations in System Design
Most candidates either skip estimation entirely or spend five minutes doing exact math. Here’s how to do quick, high-signal capacity …
Read MoreHow to List Non-Functional Requirements in System Design
Saying ’the system should be scalable and highly available’ is not an NFR. Here’s how senior engineers define NFRs that actually drive …
Read MoreHow to List Functional Requirements in System Design
Most candidates list features. Senior engineers define the system’s contract. Here’s a framework to get FRs right - with examples, …
Read MoreSQL vs NoSQL: A Practical Guide to Picking the Right Database
A deep, practical guide to SQL vs NoSQL databases. Not textbook definitions - real trade-offs, real examples, and a decision checklist that …
Read More