Uber system design interview questions

Which levels get a design round

Design questions candidates report

• Design Splitwise

  Design a wallet app where a hundred million people top up, send money to friends and pay shops. Requirements and scale, the wallet API and ledger data model, then the hard parts: atomic same-shard transfers that never go negative, cross-shard transfers with a saga and a clearing account, single-writer event sourcing for very high throughput, hot merchant accounts, holds, limits and reconciliation with the bank.

  Full walkthrough: Digital wallet

• Show every driver on a map in real time

  A senior-level design for a ride-hailing app like Uber: requirements, the math for half a million location updates a second, rider and driver APIs, a sharded in-memory supply index on hexagon cells, nearest-driver search by ETA rather than distance, matching that never double books a driver, batched matching, surge pricing per cell, a trip state machine, cell-based isolation, and trade-offs at 10x.

  Full walkthrough: Uber

• Design Dropbox

  How to design a cloud file storage and sync service like Google Drive or Dropbox: requirements, storage and traffic math, splitting files into content-addressed blocks, resumable uploads and deduplication, separating metadata from blobs, a change journal with cursors so every device syncs, push notifications, conflict handling and version history, sharing permissions, and the trade-offs.

  Full walkthrough: Google Drive Practise on the design board

• Design Messenger

  A LADDER walkthrough of a mobile chat system: requirements, scale math for 20 billion messages a day and 200 million open connections, the WebSocket and REST API, a message store partitioned by conversation, then the deep dives: routing between chat servers, offline delivery and push, sent-delivered-read receipts, per-conversation ordering, group fan-out, presence, media and end-to-end encryption.

  Full walkthrough: WhatsApp Practise on the design board

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

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