hard
Design a News Feed
The home timeline of Twitter, Instagram or Facebook: posts from people you follow, ranked, fresh, and fast for hundreds of millions of users.
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Snap system design interview questions
9 questions on this site are reported in Snap 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: fan-out, ranking, caching, social, media-pipeline, object-storage, counters, ttl, geo-sharding, recommendations, bloom-filters, match-detection, write-heavy, graph, sharding, in-memory, consistency, batch, auctions, budget-pacing, inverted-index, low-latency, short-video, prefetch, session-ranking, exploration, cdn, real-time, pub-sub, geospatial, privacy, random-walks, visual-search, deduplication, vector-search, image-serving, moderation, perceptual-hashing, review-queues, policy-engine, audit-log.
Run an AI mock Snap 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 Snap. It indicates where a question has been asked, nothing more.
Snap questions
hard
Design Instagram
Upload photos, publish posts and stories, and load a feed of them for 500 M daily users, with every image served from a CDN in milliseconds.
medium
Design Tinder
Show each person a deck of nearby profiles that fit both people’s preferences, never repeat one, take 2 billion swipes a day, and announce a match the instant two people like each other.
hard
Design a Social Graph
LinkedIn’s connections for 1 B members: invitations, follows, a 1st/2nd/3rd badge on 200 k profile views a second, and daily People You May Know.
hard
Design an Ad Serving System
Pick the best of 10 M active ads for 5 M requests a second in under 100 ms, within every campaign’s targeting, budget and frequency caps.
hard
Design TikTok
A full-screen feed of short videos for 1 B daily users, where the next clip starts instantly and every swipe reshapes what comes next.
hard
Design Nearby Friends
Show each user which friends are within 5 miles, refreshed every 30 s, for 10 M concurrent users, without leaking anyone’s location.
hard
Design Pinterest
Save images to boards, browse a personalised grid and search by picture: 100 M daily users, 5 B distinct images behind 100 B saves.
hard
Design a Content Moderation System
Catch spam, nudity, hate and illegal media in 4 billion daily posts and comments before they spread, with 15,000 reviewers for the hard cases.
What the Snap round looks like
60 minutes, product-shaped and tied to Snap features: messaging, photo and video sharing, notifications, feeds or friends on a live map.
What it is reported to weigh
- Ephemeral data: expiry and deletion built into storage, not added afterwards
- Low latency for a mobile-first app, including real-time delivery
- Large photos and videos: storage, processing and delivery through a CDN
- A design tied back to the feature and what the user sees
The common mistake
Keeping everything forever by default. Much of what Snap handles is meant to expire, and candidates are advised that this changes the architecture, so design expiry and deletion in from the start.
From public interview guides and candidate reports, and Snap’s own interview guidance where it publishes any. Not endorsed by Snap. Formats change; treat it as a prior, not a promise.
How to prepare for the Snap 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 Snap interviews under different names.
- Design a URL Shortenerkey-generation · caching · cdn
- Design Slackreal-time · websockets · fan-out
- Design a Payment Systemconsistency · idempotency · ledger
- 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 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 Search Autocompletetries · ranking · caching
- Design an Ad Click Aggregatorstream-processing · windowing · exactly-once
- 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 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 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 Redditcomment-trees · voting · ranking
- Design DoorDashstate-machine · dispatch · eta-prediction
- Design AWS Step Functionsworkflow-orchestration · event-sourcing · durable-timers
- 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 an API Gatewayapi-gateway · authentication · control-plane
- Design GitHubgit · replication · quorum
- Design Venmoledger · sharding · hot-keys
- Design a Multiplayer Game Backendreal-time · udp · game-servers
- Design Google Newsclustering · ingestion · ranking
- Design an A/B Testing Platformexperimentation · hashing · statistics
- Design GitHub Copilotlatency-budget · cancellation · prefix-caching
- Design a Fraud Detection Systemfraud · feature-store · stream-processing
- Design Pastebinobject-storage · expiry · caching
- Design a Webhook Delivery Systemwebhooks · retries · isolation
- Design a Vector Databasevector-search · ann-indexes · quantisation
- 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 Snap system design interview
What system design questions does Snap ask?
Questions reported in Snap system design interviews include News Feed, Instagram, Tinder, Social Graph, Ad Serving System, TikTok, Nearby Friends and Pinterest, among 9 in total. Between them they test fan out, ranking, caching, social, media pipeline and object storage. The reports come from public interview guides and candidate accounts, not from Snap, so practise the patterns rather than memorising one list.
What is the Snap system design interview like?
60 minutes, product-shaped and tied to Snap features: messaging, photo and video sharing, notifications, feeds or friends on a live map.
What does Snap look for in a system design interview?
Reports say the Snap round weighs 4 things. 1. Ephemeral data: expiry and deletion built into storage, not added afterwards. 2. Low latency for a mobile-first app, including real-time delivery. 3. Large photos and videos: storage, processing and delivery through a CDN. 4. A design tied back to the feature and what the user sees. Keeping everything forever by default. Much of what Snap handles is meant to expire, and candidates are advised that this changes the architecture, so design expiry and deletion in from the start.
How do I prepare for the Snap 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 News Feed: watch a strong candidate answer it turn by turn, then sit it yourself. Then cover the patterns the round leans on (fan out, ranking, caching and social) with one more question each.