hard
Design a Payment System
Accept card payments for an e-commerce platform, move money correctly exactly once, and be able to prove it.
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Stripe system design interview questions
14 questions on this site are reported in Stripe software engineer interviews. Each has a full reference design (requirements, back-of-envelope numbers, components, user flows and deep dives with interviewer follow-ups). Each one can be walked through turn by turn and then sat as a mock. Patterns covered: consistency, idempotency, ledger, fintech, consistent-hashing, eviction, replication, hot-keys, algorithms, counters, redis, edge, inventory, reservations, locking, queueing, thundering-herd, scheduling, leases, queues, fault-tolerance, order-book, determinism, event-sourcing, low-latency, fairness, id-generation, clocks, bit-layout, k-sortable, workflow-orchestration, durable-timers, sharding, api-gateway, authentication, control-plane, quotas, multi-tenancy, git, quorum, content-addressing, fraud, feature-store, stream-processing, exploration, webhooks, retries, isolation, ssrf, market-data, order-management, websockets.
Run an AI mock Stripe interview →One of these questions, run as a live round in that style, with a debrief at the end.
Attribution comes from public interview guides and candidate reports, not from Stripe. It indicates where a question has been asked, nothing more.
Stripe questions
hard
Design a Distributed Cache
A 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.
medium
Design a Rate Limiter
A distributed service that decides, in under a millisecond, whether a request from a client is allowed under its quota.
hard
Design Ticketmaster
Sell 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.
medium
Design a Distributed Job Scheduler
Run 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.
hard
Design a Stock Exchange
Match buy and sell orders in microseconds, in a strict and provable order, never lose a fill, and stay correct when the matching engine dies mid-trade.
medium
Design a Unique ID Generator
Hand 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.
hard
Design AWS Step Functions
A managed workflow engine that runs 200 M state-machine executions a day, some lasting a year, applying every transition exactly once.
hard
Design an API Gateway
One front door for public and partner APIs: authenticate, limit and route 1 M requests a second to 300 services, adding under 10 ms.
hard
Design GitHub
Host 400 M git repositories on replicated file servers, serve 100 k fetches a second, and run pull requests, forks and webhooks on top.
hard
Design Venmo
80 M users paying friends instantly: 15 M transfers a day on a sharded double-entry ledger, funded and cashed out over slow bank rails.
hard
Design a Fraud Detection System
Allow, block or challenge 10,000 card payments a second in under 100 ms, then learn from chargebacks that arrive months later.
hard
Design a Webhook Delivery System
Deliver 3 billion signed webhooks a day to a million customer endpoints, retrying for three days, without one slow endpoint delaying anyone else.
hard
Design Robinhood
A retail brokerage: live prices to 3 M phones, 20 k orders a second at the open, every share and cent exact.
What the Stripe round looks like
45–60 minutes, typically money-adjacent: correctness, idempotency and reconciliation over raw scale.
What it is reported to weigh
- Exactly-once effects, idempotency keys and retries
- Ledger and state-machine design, including the unknown-outcome case
- API design and the developer experience of the thing you are building
- Reconciliation and what happens when an external system disagrees with you
The common mistake
Optimising for throughput when the question is about never losing or double-charging a payment.
From public interview guides and candidate reports, and Stripe’s own interview guidance where it publishes any. Not endorsed by Stripe. Formats change; treat it as a prior, not a promise.
How to prepare for the Stripe system design interview
Large-company loops run 45 to 60 minutes, expect numbers, and spend most of the time on deep dives. Walk through a question to see how a strong candidate paces the hour, sit the same question as a mock until you can produce the requirements, the estimates and the design without looking, then read the interview framework guide for how to structure the hour. The other questions on the site teach patterns that show up in Stripe interviews under different names.
- Design a URL Shortenerkey-generation · caching · cdn
- Design Slackreal-time · websockets · fan-out
- Design a News Feedfan-out · ranking · caching
- Design YouTubetranscoding · cdn · adaptive-bitrate
- Design Google Mapsgeospatial · routing · graphs
- Design a Matchmaking Systemqueues · scheduling · latency
- Design Ubergeospatial · matching · streaming
- Design a Notification Systemfan-out · multi-channel · idempotency
- Design Google Docscrdt · operational-transform · websockets
- Design an LLM Inference Servicegpu-batching · streaming · scheduling
- Design ChatGPTstreaming · tool-calling · context-management
- Design a Web Crawlerfrontier · politeness · dedupe
- Design Dropboxchunking · dedupe · sync
- Design Search Autocompletetries · ranking · caching
- Design an Ad Click Aggregatorstream-processing · windowing · exactly-once
- Design a Project-to-Contractor Matching Systemrecommendations · ranking · marketplace
- Design Instagrammedia-pipeline · object-storage · fan-out
- Design WhatsApppersistent-connections · store-and-forward · end-to-end-encryption
- Design Netflixcdn · proactive-caching · adaptive-bitrate
- Design Yelpgeospatial-index · search · ranking
- Design a Real-Time Leaderboardsorted-sets · ranking · sharding
- Design a Distributed Key-Value Storeconsistent-hashing · quorum-replication · conflict-resolution
- Design LeetCodesandboxing · job-queue · untrusted-code
- Design Airbnbavailability-search · inventory · double-booking
- Design a Distributed Message Queueappend-only-log · partitioning · replication
- Design a Metrics and Monitoring Systemtime-series · compression · cardinality
- Design Tindergeo-sharding · recommendations · bloom-filters
- Design Redditcomment-trees · voting · ranking
- Design DoorDashstate-machine · dispatch · eta-prediction
- Design Apache Airflowworkflow-orchestration · dag-scheduling · backfills
- Design Zapierworkflow-orchestration · polling · webhooks
- Design an Online Auctioncontention · compare-and-set · durable-timers
- Design Live Commentsbroadcast · pub-sub · sse
- Design a Top-K Heavy Hitters Serviceheavy-hitters · count-min-sketch · sliding-windows
- Design Zoomwebrtc · sfu · real-time-media
- Design Google Searchinverted-index · scatter-gather · tail-latency
- Design Spotifyprefetching · licensing · offline
- Design Gmailsmtp-ingress · spam-filtering · per-user-sharding
- Design Amazonshopping-cart · inventory · caching
- Design a Large File Distribution Systempeer-to-peer · chunking · bandwidth
- Design a Recommendation Systemrecommendations · ranking · vector-search
- Design a Distributed Lock Serviceconsensus · leases · fencing-tokens
- Design an Object Storage Serviceerasure-coding · range-partitioning · durability
- Design Google Calendarrecurrence · time-zones · fan-out
- Design a Code Deployment Systemdeployment · canary · reconciliation
- Design a Distributed Logging Systemlog-aggregation · inverted-index · tiered-storage
- Design Twitchlive-video · low-latency · transcoding
- Design a Price Trackeradaptive-scheduling · change-detection · time-series
- Design Stravageospatial · async-pipeline · spatial-matching
- Design Post Searchsearch · real-time · privacy
- Design Figmamultiplayer · last-writer-wins · websockets
- Design a Load Balancerload-balancing · networking · consistent-hashing
- Design a RAG Systemrag · vector-search · hybrid-search
- Design a CDNcdn · anycast · tiered-cache
- Design a Social Graphgraph · sharding · in-memory
- Design an Ad Serving Systemauctions · budget-pacing · ranking
- Design a Multiplayer Game Backendreal-time · udp · game-servers
- Design TikTokshort-video · prefetch · session-ranking
- Design Google Newsclustering · ingestion · ranking
- Design an A/B Testing Platformexperimentation · hashing · statistics
- Design GitHub Copilotlatency-budget · cancellation · prefix-caching
- Design Nearby Friendsreal-time · pub-sub · fan-out
- Design Pastebinobject-storage · expiry · caching
- Design Pinterestrandom-walks · visual-search · deduplication
- Design a Vector Databasevector-search · ann-indexes · quantisation
- Design a Content Moderation Systemmoderation · perceptual-hashing · review-queues
- Design a Flight Booking Systemfan-out · caching · saga
- Design a Container Orchestratorscheduling · reconciliation · consensus
- Design Discordreal-time · fan-out · actors
Questions people ask about the Stripe system design interview
What system design questions does Stripe ask?
Questions reported in Stripe system design interviews include Payment System, Distributed Cache, Rate Limiter, Ticketmaster, Distributed Job Scheduler, Stock Exchange, Unique ID Generator and AWS Step Functions, among 14 in total. Between them they test consistency, idempotency, ledger, fintech, consistent hashing and eviction. The reports come from public interview guides and candidate accounts, not from Stripe, so practise the patterns rather than memorising one list.
What is the Stripe system design interview like?
45–60 minutes, typically money-adjacent: correctness, idempotency and reconciliation over raw scale.
What does Stripe look for in a system design interview?
Reports say the Stripe round weighs 4 things. 1. Exactly-once effects, idempotency keys and retries. 2. Ledger and state-machine design, including the unknown-outcome case. 3. API design and the developer experience of the thing you are building. 4. Reconciliation and what happens when an external system disagrees with you. Optimising for throughput when the question is about never losing or double-charging a payment.
How do I prepare for the Stripe system design interview?
Practise the questions reported there out loud, under a 45-minute clock: requirements with numbers first, then estimates, a high-level design, and deep dives into the two or three hardest parts. Start with Payment System: watch a strong candidate answer it turn by turn, then sit it yourself. Then cover the patterns the round leans on (consistency, idempotency, ledger and fintech) with one more question each.