Practice
Work through real interview questions
Each solution walks the four-step approach (use cases, high-level design, core components, scaling) and links back to the concepts it relies on.
System design
Open-ended architecture questions with diagrams, estimates and trade-offs.
Design Mint.com
Pull in transactions from many banks, categorise spending and send budget alerts.
Intermediate10 min read
Design Pastebin.com (or Bit.ly)
A URL-shortening and text-sharing service: hashing, expiry and read-heavy traffic.
Starter8 min read
Design a key-value cache to save the results of the most recent web server queries
A key-value store that fronts a search engine and evicts with LRU.
Intermediate6 min read
Design Amazon's sales rank by category feature
Compute the best-selling products per category from a stream of orders.
Intermediate7 min read
Design a system that scales to millions of users on AWS
Grow from one box to millions of users, one bottleneck at a time.
Advanced10 min read
Design the data structures for a social network
Shortest path and friend-of-friend queries over a very large social graph.
Intermediate7 min read
Design the Twitter timeline and search
Timeline fan-out, a home feed and search for hundreds of millions of users.
Advanced9 min read
Design a web crawler
Crawl billions of links without repeating work, then rank and serve the results.
Intermediate8 min readObject-oriented design
Model the objects, then write the code. Python solutions with the reasoning alongside.
Design a call center
Route calls through operators, supervisors and directors.
2 min read02Design a deck of cards
Model cards, hands and a generic deck, then a game of blackjack.
1 min read03Design a hash map
Build a hash map: hashing, buckets and collision handling.
1 min read04Design an LRU cache
A least-recently-used cache with a linked list and a lookup table.
1 min read05Design an online chat
Users, chats, requests and messages for a chat server.
1 min read06Design a parking lot
Vehicles, spots and levels for a multi-level parking garage.
2 min read