2. Design a Distributed Rate Limiter
Enforce tenant quotas across servers while making burst behavior and outage policy explicit.
ClassicMedium
Guided practice
Start with a template. Work through each step. Ask Coach when you need a second opinion.
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- Practice briefStart with your own approach
14. Sell a limited drop without overselling
Separate reservation, payment and confirmed purchase during a 50,000-person launch.
Product & backendMedium - Practice briefStart with your own approach
26. Share one study room without double bookings
Explain a simple booking process, try it with examples and improve one weak spot.
FoundationsEasy 37. Reservation with a TTL, and a Unique Constraint
Scarce inventory — a seat, a room, the last unit — with far more buyers than units. Holding a database row for the minutes someone takes to pay does not scale, and checking availability before writing is a race that sells the same seat twice.
Product & backendMedium48. Design a Ticket Booking System like Ticketmaster
Hold seats with one conditional write, pay by authorize and capture, and put ten million fans in a fair waiting room without selling a seat twice.
ClassicMedium49. Design an Online Auction like eBay
Take bids on 10 million live auctions with one consistent highest bid, lose none, push the price to every watcher and end each auction fairly.
ClassicMedium62. Design a Flash Sale System
Sell 10,000 units to a million people at noon with a lottery waiting room, a Redis gate before an Aurora ledger and holds that expire.
ClassicMedium64. Design for Contention: Thousands Racing for the Same Item
Design for contention through a limited sneaker drop: row locks, conditional writes, expiring holds, fencing tokens, sagas and one writer per item.
ClassicMedium78. Design a Coordination Service like ZooKeeper
A coordination service like ZooKeeper: znodes, sessions and watches, a ZAB quorum of five with observers, and the recipes for elections and locks.
ClassicMedium