Salesforce system design interview questions

Which levels get a design round

Design questions candidates report

• Celebrity fan-out in a social feed

  How to design a ranked social news feed for a billion daily users: scope, traffic and memory math for per-user inboxes, the feed API and data model, fan-out of friend posts through an event stream, candidate generation and multi-stage ranking, privacy filtering at read time, seen-state and new-post signals, and the trade-offs you should name.

  Full walkthrough: News Feed Practise on the design board

• Ticket booking

  Design a ticket booking app where thousands of people fight over the same few hundred seats. Requirements and scale, the booking API and seat data model, then the hard parts: atomic multi-seat holds with expiry, optimistic versus pessimistic locking, tying payment to a hold without double booking, a virtual waiting room for blockbuster releases, live seat maps, and the trade-offs.

  Full walkthrough: Movie booking

• Rate limiter

  A LADDER walkthrough of a rate limiter shared by many gateway servers: requirements, scale math for half a million requests a second and ten million keys, the rule and response API, Redis state, then the deep dives: choosing token bucket, atomic updates with a Lua script, keeping the added latency under a millisecond, sharding and hot keys, failing open, multiple regions and rolling out new rules safely.

  Full walkthrough: Rate limiter Practise on the design board

Also reported

• Connection pool (LLD)
• Marketing campaign system
• Parking lot

How to answer any design question: the LADDER method · How the design round is scored by level · Low-level design and machine coding

Questions people ask