Mock system design interview at Uber

The interviewer’s opening question is free. Answering it is part of Pro. See an example round and its debrief →

• Design a Payment SystemAccept card payments for an e-commerce platform, move money correctly exactly once, and be able to prove it.
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• Design Google MapsMap tiles, place search, turn-by-turn routing with live traffic, and ETAs for a billion users.
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• Design UberMatch riders with nearby drivers in seconds, track trips live, and price them, for millions of concurrent users worldwide.
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• Design a Notification SystemDeliver push, email, SMS and in-app notifications to hundreds of millions of users: the right channel, once, on time, and never at 3 a.m.
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• Design a Distributed CacheA Redis-like cache as a service: hundreds of nodes, terabytes of memory, sub-millisecond gets, and a cluster that survives losing a machine mid-request.
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• Design a Rate LimiterA distributed service that decides, in under a millisecond, whether a request from a client is allowed under its quota.
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• Design TicketmasterSell 60 000 seats in ten minutes to a million people at once: hold a seat while someone pays, never sell it twice, and keep the site up when demand is a hundred times supply.
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• Design a Distributed Job SchedulerRun millions of cron jobs and one-off tasks on time across a fleet, exactly once each, and keep going when a worker dies halfway through one.
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• Design WhatsAppDeliver 50 billion end-to-end encrypted messages a day to phones that are often offline, with sent, delivered and read ticks, and a server that cannot read any of it.
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• Design YelpFind the best places near you, filtered by what is open now, from 200 M businesses, in under 200 ms, and keep ratings honest as reviews arrive.
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• Design a Unique ID GeneratorHand out a million 64-bit ids a second across many hosts and regions, never twice, roughly in time order, with no central bottleneck and no trust in the wall clock.
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• Design AirbnbSearch 7 M listings by place, dates and price, book a stay without ever selling the same night twice, and keep calendars in sync with hosts’ other platforms.
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• Design a Distributed Message QueueA Kafka-style log that ingests a million messages a second, keeps them in order per key, replicates them so no acknowledged message is lost, and lets many consumer groups read at their own pace.
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• Design a Metrics and Monitoring SystemIngest 10 million samples a second from 100,000 hosts, keep them queryable for a year at shrinking resolution, draw dashboards in under a second, and page the right person within a minute.
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• Design DoorDashTake a food order, get a restaurant to cook it and a courier to arrive just as it is ready, and keep three parties in sync across millions of orders a day.
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• Design AWS Step FunctionsA managed workflow engine that runs 200 M state-machine executions a day, some lasting a year, applying every transition exactly once.
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• Design Apache AirflowSchedule and run twenty thousand data pipelines as dependency graphs, each run tied to a slice of time, so a failed night can be retried or a year backfilled safely.
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• Design a Distributed Lock ServiceA Chubby-style lock service for 50 k processes: leases, leader election, fencing tokens and watched config, never letting two holders act at once.
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• Design a Code Deployment SystemBuild each merge once into a signed artifact, roll it out in stages to 50,000 hosts in 10 regions, and roll back automatically on regression.
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• Design a Distributed Logging SystemCollect 10 million log lines a second from 100,000 hosts, make them searchable within seconds, stream them live, and keep a year affordably.
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• Design StravaRecord runs and rides offline, process each upload into a map, stats and segment efforts, and rank them for 100 M athletes.
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• Design a Load BalancerSpread 5 M requests a second over 50 k backends, terminate TLS, route by host and path, survive losing any balancer or data centre.
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• Design an API GatewayOne front door for public and partner APIs: authenticate, limit and route 1 M requests a second to 300 services, adding under 10 ms.
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• Design an A/B Testing PlatformRun 500 experiments at once on 300 M users: sticky variants in microseconds, exposure logging, and confidence intervals teams can trust.
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• Design Nearby FriendsShow each user which friends are within 5 miles, refreshed every 30 s, for 10 M concurrent users, without leaking anyone’s location.
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• Design a Fraud Detection SystemAllow, block or challenge 10,000 card payments a second in under 100 ms, then learn from chargebacks that arrive months later.
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• Design a Flight Booking SystemAnswer 50 M searches a day from 20 slow, metered suppliers through a fare cache, then book seats you do not own, exactly once.
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• Design a Container OrchestratorPlace 300,000 containers on 10,000 machines from declared desired state, keep them running through failures, and give every service a stable address.
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