hard
Design YouTube
Upload, transcode, and stream video to a billion viewers: a processing pipeline on one side, a CDN problem on the other.
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Netflix system design interview questions
11 questions on this site are reported in Netflix 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: transcoding, cdn, adaptive-bitrate, pipelines, storage, tries, ranking, caching, search, stream-processing, windowing, exactly-once, olap, analytics, proactive-caching, steering, resilience, workflow-orchestration, event-sourcing, durable-timers, sharding, leases, recommendations, vector-search, feature-store, real-time, deployment, canary, reconciliation, rollback, blast-radius, live-video, low-latency, request-coalescing, anycast, tiered-cache, cache-invalidation, multi-tenancy, api-gateway, authentication, control-plane, quotas, experimentation, hashing, statistics.
Run an AI mock Netflix 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 Netflix. It indicates where a question has been asked, nothing more.
Netflix questions
medium
Design Search Autocomplete
Suggest the top ten completions after every keystroke, in under fifty milliseconds, from what the world searched for in the last hour, without suggesting anything that gets you in the newspaper.
hard
Design an Ad Click Aggregator
Count a million ad clicks a second, show advertisers a dashboard that is seconds behind, stop a campaign the moment its budget runs out, and be exactly right when the invoice is cut.
hard
Design Netflix
Stream a fixed catalog to 40 M people at once, 200 Tbps at peak, starting in under two seconds, from cache servers placed inside the viewers’ own internet providers.
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 a Recommendation System
The “recommended for you” video home feed: 50 personalised videos picked from billions for 500 M daily users in under 200 ms.
hard
Design a Code Deployment System
Build 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.
hard
Design Twitch
Ingest 100 k live broadcasts, transcode them in real time, and deliver each about three seconds behind live, to three viewers or 500 k.
hard
Design a CDN
A multi-tenant CDN for 30 M customer domains: 300 PoPs, 50 M requests a second served mostly from cache, and global purges in seconds.
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 an A/B Testing Platform
Run 500 experiments at once on 300 M users: sticky variants in microseconds, exposure logging, and confidence intervals teams can trust.
What the Netflix round looks like
45–60 minutes, often on streaming delivery, the data platform behind it, or a high-volume service such as search or ad events.
What it is reported to weigh
- Availability first: what keeps playing when a dependency fails
- Content delivery: CDN placement, caching and the cost of bytes moved
- Event pipelines at very high volume, and what has to be exact versus approximate
- Operating it: resilience testing, regional failover and observability
The common mistake
Spending the hour on the metadata service. The bytes, the CDN and what happens when a region goes down are what the interviewer wants to hear about.
From public interview guides and candidate reports, and Netflix’s own interview guidance where it publishes any. Not endorsed by Netflix. Formats change; treat it as a prior, not a promise.
How to prepare for the Netflix 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 Netflix interviews under different names.
- Design a URL Shortenerkey-generation · caching · cdn
- Design Slackreal-time · websockets · fan-out
- Design a Payment Systemconsistency · idempotency · ledger
- Design a News Feedfan-out · ranking · caching
- 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 Distributed Cacheconsistent-hashing · eviction · replication
- Design a Web Crawlerfrontier · politeness · dedupe
- Design a Rate Limiteralgorithms · counters · redis
- Design Dropboxchunking · dedupe · sync
- Design Ticketmasterinventory · reservations · locking
- Design a Distributed Job Schedulerscheduling · leases · idempotency
- Design a Stock Exchangeorder-book · determinism · event-sourcing
- 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 Yelpgeospatial-index · search · ranking
- Design a Real-Time Leaderboardsorted-sets · ranking · sharding
- Design a Distributed Key-Value Storeconsistent-hashing · quorum-replication · conflict-resolution
- Design a Unique ID Generatorid-generation · clocks · leases
- 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 Distributed Lock Serviceconsensus · leases · fencing-tokens
- Design an Object Storage Serviceerasure-coding · range-partitioning · durability
- Design Google Calendarrecurrence · time-zones · fan-out
- Design a Distributed Logging Systemlog-aggregation · inverted-index · tiered-storage
- 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 Social Graphgraph · sharding · in-memory
- Design an Ad Serving Systemauctions · budget-pacing · ranking
- Design GitHubgit · replication · quorum
- Design Venmoledger · sharding · hot-keys
- Design a Multiplayer Game Backendreal-time · udp · game-servers
- Design TikTokshort-video · prefetch · session-ranking
- Design Google Newsclustering · ingestion · ranking
- Design GitHub Copilotlatency-budget · cancellation · prefix-caching
- Design Nearby Friendsreal-time · pub-sub · fan-out
- Design a Fraud Detection Systemfraud · feature-store · stream-processing
- Design Pastebinobject-storage · expiry · caching
- Design a Webhook Delivery Systemwebhooks · retries · isolation
- Design Pinterestrandom-walks · visual-search · deduplication
- Design a Vector Databasevector-search · ann-indexes · quantisation
- Design a Content Moderation Systemmoderation · perceptual-hashing · review-queues
- Design Robinhoodmarket-data · order-management · ledger
- 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 Netflix system design interview
What system design questions does Netflix ask?
Questions reported in Netflix system design interviews include YouTube, Search Autocomplete, Ad Click Aggregator, Netflix, AWS Step Functions, Recommendation System, Code Deployment System and Twitch, among 11 in total. Between them they test transcoding, cdn, adaptive bitrate, pipelines, storage and tries. The reports come from public interview guides and candidate accounts, not from Netflix, so practise the patterns rather than memorising one list.
What is the Netflix system design interview like?
45–60 minutes, often on streaming delivery, the data platform behind it, or a high-volume service such as search or ad events.
What does Netflix look for in a system design interview?
Reports say the Netflix round weighs 4 things. 1. Availability first: what keeps playing when a dependency fails. 2. Content delivery: CDN placement, caching and the cost of bytes moved. 3. Event pipelines at very high volume, and what has to be exact versus approximate. 4. Operating it: resilience testing, regional failover and observability. Spending the hour on the metadata service. The bytes, the CDN and what happens when a region goes down are what the interviewer wants to hear about.
How do I prepare for the Netflix 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 YouTube: watch a strong candidate answer it turn by turn, then sit it yourself. Then cover the patterns the round leans on (transcoding, cdn, adaptive bitrate and pipelines) with one more question each.