Design a Real-Time Leaderboard - System Design
Everyone thinks a leaderboard is a SELECT ... ORDER BY score DESC LIMIT 100. “Store the scores, sort them, return the top 100, done.” Then …
Read MoreDesign a Web Crawler - System Design
Everyone starts a web crawler the same way: a queue of URLs, a while loop, fetch, parse out the links, push them back on the queue, repeat. …
Read MoreDesign an Ad Click Aggregator - System Design
Everyone thinks an ad click aggregator is a SELECT COUNT(*) ... GROUP BY ad_id. “Log every click, count the rows, show the advertiser their …
Read MoreHow to Interview for an AI Engineer Role in 2026
If you prep for an AI engineer interview by grinding gradient descent derivations and softmax cross-entropy, you will walk in ready for a …
Read MoreDesign BookMyShow / a Ticket Booking System - System Design
“Design BookMyShow” looks like a catalogue app: list cities, list movies, list showtimes, take a payment, print a QR code. The interviewer …
Read MoreDesign Dropbox / a File Sync and Storage Service - System Design
A file sync service sounds like a glorified upload button until you count the bytes. The naive version is a single PUT /file that stores a …
Read MoreDesign Search Autocomplete / Typeahead - System Design
Everyone thinks autocomplete is a LIKE 'prefix%' query. “Index the search terms, run a prefix match, return the top ten, done.” Then the …
Read MoreREITs vs InvITs in India - Where the Yield Actually Comes From
Most people buy a REIT or an InvIT because a screener showed a 6% or a 12% yield next to it, and 12% looks like a fixed deposit that quietly …
Read MoreDesign a Distributed Cache (like Redis) - System Design
Everyone thinks a cache is a hash map with a size cap. “Store key-value pairs in RAM, evict when it fills up, done.” Then the interviewer …
Read MoreDesign a Payment System / Digital Wallet - System Design
“Move 500 rupees from Alice to Bob” sounds like an UPDATE statement. Then you think about it. What if the request times out and the client …
Read MoreDesign Google Docs / Collaborative Editing - System Design
A document editor sounds trivial until you put two people in the same document. One editor is a text box that saves to a database: type, PUT …
Read MorePostgres Is Still Eating Your Stack - The 2026 Extension Edition
Most “just use Postgres for everything” posts stop at the fun part. They show you that pgvector exists, that SKIP LOCKED gives you a queue, …
Read MoreDesign a Notification System (Push, Email, SMS) - System Design
“Send the user a notification” sounds like one function call. Then you write it down. Which channel - push, email, SMS, in-app? What if the …
Read MoreDesign a Rate Limiter - System Design
Everyone thinks the rate limiter is a for-loop with a counter. “Count requests per user per minute, reject when it goes over 100, done.” …
Read MoreDesign 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 MoreGuardrails for LLM Apps - The Layers Between the Model and the User
The most common mistake in LLM apps is treating the model as the safety layer. You write a careful system prompt, add “do not answer …
Read MoreSpec-Driven Development - Writing the Spec Is Writing the Code Now
The most productive engineers I know stopped bragging about how fast they type. When a coding agent can produce 400 lines of correct code …
Read MoreChoosing an Embedding Model in 2026 - It's Not the Leaderboard
Most teams pick an embedding model the same way they pick a sorting algorithm: look up the benchmark, take the top result, ship it. For …
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 …
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