Messaging System (Chat) Low-Level Design
6 min read Requirements One-on-one messaging and group chats (up to 500 members) Real-time message delivery (< 100ms), offline message storage, read receipts […] Read article
System Design
System Design
Content Delivery Network (CDN) Low-Level Design
6 min read What a CDN Does A Content Delivery Network caches content at edge Points of Presence (PoPs) geographically close to users, Read article
Algorithms, Coding Interview Questions
Prefix Sum Interview Patterns
5 min read Core Idea Build a prefix array where prefix[i] = arr[0] + arr[1] + … + arr[i-1]. Then any range sum Read article
System Design
Video Streaming Platform (YouTube/Netflix) Low-Level Design
6 min read Upload Pipeline Raw video upload → object storage (S3 raw bucket) → message published to transcoding queue (SQS/Kafka) → transcoding Read article
System Design
File Storage System (Google Drive / Dropbox) Low-Level Design
6 min read Requirements Design a file storage system like Google Drive or Dropbox supporting: Upload and download files up to 50 GB Read article
System Design
Ride-Sharing App (Uber/Lyft) High-Level System Design
6 min read Core Services A ride-sharing platform like Uber or Lyft decomposes into focused microservices: Location Service: ingests driver GPS pings, maintains Read article
System Design
Social Graph System Low-Level Design
7 min read Two Graph Models The first design decision is the relationship model: Directed graph (Twitter/Instagram follow): A follows B does not Read article
Algorithms, Coding Interview Questions, System Design
Object-Oriented Design Patterns for Coding Interviews
7 min read Design patterns appear in coding interviews in two ways: the interviewer asks you to implement a specific pattern, or you’re Read article
System Design
Typeahead Search (Autocomplete) System Low-Level Design
6 min read Typeahead search (also called autocomplete) is one of the most latency-sensitive features in a modern product. Users expect suggestions to Read article
System Design
E-Commerce Platform Low-Level Design
6 min read An e-commerce platform touches nearly every backend concept that appears in system design interviews: relational data modeling, inventory consistency, distributed Read article
Algorithms, Coding Interview Questions, Dynamic Programming
Stock Trading Dynamic Programming Interview Patterns
7 min read Stock trading dynamic programming problems are a classic interview cluster. Every variant – one transaction, unlimited, at most k, cooldown, Read article
System Design
Proximity Service (Find Nearby) Low-Level Design
8 min read A proximity service answers “find all restaurants / drivers / users within R km of this location” with low latency Read article
System Design
Ticket Booking System Low-Level Design
9 min read A ticket booking system like Ticketmaster must handle concurrent seat selection, hold expiry, payment confirmation, and flash sale traffic spikes. Read article
Algorithms, Coding Interview Questions, Dynamic Programming
Dynamic Programming on Intervals Interview Patterns
9 min read What is Interval DP? Interval DP is a dynamic programming pattern where you optimize over all sub-intervals of a range. Read article
System Design
Gaming Leaderboard System Low-Level Design
8 min read Requirements A gaming leaderboard system must support: Update a player’s score in real-time (on match completion) Query a player’s current Read article