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Draw your system on a canvas, watch traffic flow through it, and get instant AI feedback on exactly where your design breaks under pressure. Practice like it's the real interview.

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Built for engineers interviewing at

Google
Microsoft
Stripe
Airbnb
Meta
Adobe
OpenAI
Reddit
Google
Microsoft
Stripe
Airbnb
Meta
Adobe
OpenAI
Reddit

Why SysDes

Ship interview-ready designs
with evidence, not arrows

Run production-style load through your topology, see real bottlenecks on the canvas, and get a clear score that tells you exactly what to improve.

36

+

Infrastructure components

5

areas

AI scoring dimensions

35+

problems

Real interview questions

45

min

Full interview practice

Open the studioSee how scoring works
Live traffic simulationInstant bottleneck feedback

Platform

Everything you need to pass the loop

Design, simulate, score, and practice interviews — all in one studio, no tab switching.

36 infrastructure components

DNS, CDN, load balancers, Kafka, Redis, SQL — everything you need, ready to place and connect.

Try it free

Live traffic simulation

Watch traffic move through your diagram and see exactly where it slows down or breaks.

Try it free

AI architect

Optional Gemini challenges assumptions on the canvas — bring your own API key.

Try it free

Trade-offs & patterns

Per-component interview tips plus built-in comparison cards — SQL vs NoSQL, push vs pull, and more.

14 comparison cards
Try it free

Interview mode & scoring

Practice a full 45-minute interview with six timed phases, then get an AI score on five key areas.

6 interview phases5 score areas
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Practice bank

35 system design problems

Easy to Hard — open any card and land in the studio with the full prompt, requirements, and hints loaded.

35 problems in view

Easy

URL Shortener

Design a URL shortening service like Bitly or TinyURL. Users submit long URLs and receive short, unique aliases that redirect to the original destination. The system is heavily read-biased — for every URL created, expect 100x more redirect lookups. Real-world services like Bitly handle billions of redirects per month with sub-100ms latency, making caching strategy the key design decision.

StorageCachingHashing
Google ·Meta ·Amazon
100K reads/s100ms p99
Open
Hard

Twitter / News Feed

Design a social media feed like Twitter (X). Users can post tweets, follow others, and see a personalized timeline ranked by relevance. The core challenge is fan-out: when a celebrity with 50M followers posts a tweet, how do you deliver it to all their followers' timelines without melting your infrastructure? Real systems like Twitter use a hybrid approach — pre-computing timelines for most users while handling high-follower accounts differently.

Fan-outCacheTimeline
Twitter ·Meta ·LinkedIn
100K reads/s200ms p99
Open
Hard

Chat System

Design a real-time chat application like WhatsApp, Slack, or Discord. Support 1:1 messaging, group chats with up to 1000 members, read receipts, typing indicators, and online presence. Messages must be delivered reliably and in order, even when users switch between devices. WhatsApp processes over 100 billion messages per day — the key challenges are maintaining persistent connections at scale and guaranteeing exactly-once delivery.

WebSocketMessagingReal-time
Meta ·Slack ·Microsoft
50K reads/s50ms p99
Open
Hard

Uber / Ride Sharing

Design a ride-sharing platform like Uber or Lyft. Match riders with nearby drivers in real-time, track live location updates, calculate accurate ETAs, and handle dynamic surge pricing. The system must ingest millions of location updates per second from active drivers while simultaneously running proximity queries to match riders. Uber processes over 1 million location updates per second during peak hours, making geospatial indexing and real-time stream processing the central design challenges.

Geo-spatialReal-timeMatching
Uber ·Lyft ·Google
80K reads/s100ms p99
Open
Hard

YouTube / Video Streaming

Design a video streaming platform like YouTube or Netflix. Support video upload, transcoding into multiple formats and resolutions, globally distributed storage, and adaptive bitrate streaming to millions of concurrent viewers. YouTube serves over 1 billion hours of video daily — the key challenges are building an efficient upload-transcode-serve pipeline, leveraging CDN edge caching for popular content, and separating the fast metadata path from the slow video delivery path.

StreamingCDNTranscoding
Google ·Netflix ·Meta
200K reads/s200ms p99
Open
Easy

Rate Limiter

Design a distributed rate limiting service that throttles API requests per client, IP, or API key. Real systems like Cloudflare and AWS WAF use token bucket or sliding window algorithms backed by distributed counters in Redis. The key challenge is achieving consistency across multiple rate limiter instances without adding significant latency to the request path — Stripe processes hundreds of millions of API calls per day while enforcing per-key rate limits with sub-millisecond overhead.

DistributedAlgorithmRedis
Google ·Meta ·Amazon
50K reads/s5ms p99
Open
Medium

Notification System

Design a scalable notification service like Firebase Cloud Messaging or AWS SNS that delivers push notifications, emails, and SMS to hundreds of millions of users. The system must handle priority-based routing, template rendering, delivery tracking, and retry logic across multiple channels. Firebase Cloud Messaging delivers over 1 trillion push notifications per year — the key challenges are fan-out at scale, rate limiting per channel, and maintaining delivery guarantees without overwhelming downstream providers.

PushQueueFanout
Meta ·Google ·Amazon
50K reads/s500ms p99
Open
Medium

Typeahead / Autocomplete

Design a search autocomplete system like Google's search suggestions or Algolia's instant search. As users type each character, the system returns the top 5-10 matching suggestions ranked by popularity, personalization, and recency within 100ms. Google processes over 8.5 billion searches per day with autocomplete triggering on every keystroke — the core challenges are building an efficient prefix-matching data structure (trie) and keeping suggestions fresh as search trends change in real-time.

TrieSearchCaching
Google ·Meta ·LinkedIn
200K reads/s50ms p99
Open
Medium

Web Crawler

Design a distributed web crawler like Googlebot that can crawl billions of web pages efficiently. The crawler must manage a URL frontier, respect robots.txt politeness policies, deduplicate content, and handle the enormous variety of web page structures. Google's crawler discovers and indexes trillions of URLs and maintains an index of over 400 billion pages — the key design decisions involve URL prioritization, politeness (not overwhelming any single domain), and distributed coordination to avoid redundant crawls.

DistributedQueueStorage
Google ·Microsoft ·Amazon
10K reads/s1000ms p99
Open
Medium

Distributed Cache

Design a distributed in-memory caching system like Redis or Memcached. The system must support key-value storage with sub-millisecond reads, consistent hashing for data distribution, multiple eviction policies, and replication for fault tolerance. Redis can serve hundreds of thousands to over 1 million requests per second per node on optimized hardware — the key challenges are maintaining cache coherence across nodes, handling hot keys that receive disproportionate traffic, and designing a partition strategy that minimizes data movement during scaling events.

HashingReplicationMemory
Amazon ·Google ·Microsoft
500K reads/s2ms p99
Open
Hard

Payment System

Design a payment processing platform like Stripe or PayPal. The system handles payment authorization, capture, settlement, refunds, and ledger management with strict financial consistency guarantees. Stripe processes nearly $2 trillion annually — the core challenges are ensuring exactly-once payment execution through idempotency keys, maintaining a double-entry accounting ledger, and handling the complex state machine of payment lifecycles across multiple payment processors and methods.

ACIDIdempotentLedger
Stripe ·PayPal ·Google
30K reads/s200ms p99
Open
Hard

Ticket Booking (Ticketmaster)

Design a ticket booking platform like Ticketmaster or BookMyShow for concerts, sports events, and shows. The system must handle massive traffic spikes when popular events go on sale (Taylor Swift's Eras Tour saw 14 million users hit the site simultaneously), manage seat inventory with optimistic locking to prevent double-booking, and implement a virtual waiting room queue. The central challenges are handling extreme concurrency on hot inventory, seat hold/release lifecycle management, and preventing bots from buying tickets.

ConcurrencyInventoryBooking
Amazon ·Airbnb ·Google
200K reads/s200ms p99
Open
Hard

Google Docs / Collaborative Editor

Design a real-time collaborative document editor like Google Docs or Notion where multiple users can simultaneously edit the same document with changes appearing instantly for all participants. Google Docs supports up to 100 concurrent editors on a single document — the core challenges are conflict resolution when two users edit the same paragraph simultaneously (using Operational Transformation or CRDTs), maintaining cursor positions and selections across participants, and ensuring document state eventually converges to the same result regardless of network delays.

CRDTWebSocketCollaboration
Google ·Microsoft ·Notion
50K reads/s100ms p99
Open
Hard

Dropbox / File Storage

Design a cloud file storage and synchronization service like Dropbox or Google Drive. Users upload files that sync across all their devices, with support for file versioning, sharing, and conflict resolution. Dropbox syncs over 1.2 billion files daily — the key engineering challenges are efficient delta sync (only uploading changed blocks instead of entire files), deduplication across users to save storage, and handling conflicts when the same file is edited on multiple devices while offline.

ChunkingSyncDedup
Dropbox ·Google ·Amazon
50K reads/s500ms p99
Open
Easy

Parking Lot System

Design a smart parking lot management system that tracks vehicle entry/exit, manages spot availability in real-time, handles reservations, and processes payments. Modern smart parking systems like ParkMobile and SpotHero serve hundreds of millions of annual transactions — the key challenges are maintaining accurate real-time availability across multiple lots, handling concurrent reservation requests for the same spot, and integrating with IoT sensors for automatic occupancy detection.

IoTReal-timeBooking
Amazon ·Google ·Uber
5K reads/s200ms p99
Open
Medium

Instagram / Photo Sharing

Design a photo and short-video sharing platform like Instagram. Users upload photos that are processed (resized, filtered, compressed), stored across a CDN, and displayed in a personalized feed. Instagram serves over 3 billion monthly active users and processes 100+ million photo uploads daily — the key challenges are building an efficient media processing pipeline, generating a ranked feed from thousands of candidate posts, and serving media globally with minimal latency using edge caching.

CDNMediaFeed
Meta ·Google
150K reads/s200ms p99
Open
Medium

Spotify / Music Streaming

Design a music streaming platform like Spotify that serves audio content to millions of concurrent listeners, manages a catalog of 100M+ tracks, generates personalized playlists, and supports offline downloads. Spotify streams billions of minutes of audio daily — the key challenges are optimizing audio delivery with adaptive bitrate streaming, building a recommendation engine from listening history, and managing music licensing and royalty tracking for artists.

StreamingCDNRecommendations
Spotify ·Apple ·Amazon
100K reads/s200ms p99
Open
Hard

Amazon / E-Commerce

Design a large-scale e-commerce platform like Amazon. The system handles product catalog management with millions of SKUs, shopping cart persistence, inventory tracking across warehouses, order processing, and personalized recommendations. Amazon processes over 300 million active customer accounts and handles millions of orders per hour during peak events like Prime Day — the central challenges are maintaining inventory consistency across concurrent purchases, building a low-latency product search, and orchestrating the complex order fulfillment pipeline.

CatalogCartInventory
Amazon ·Stripe ·Google
200K reads/s200ms p99
Open
Hard

Slack / Team Messaging

Design a workspace-based team messaging platform like Slack or Microsoft Teams. The system supports organized channels, threaded conversations, direct messages, file sharing, search across message history, and integrations with third-party services. Slack handles tens of millions of daily active users across hundreds of thousands of workspaces — the key challenges are maintaining message ordering and delivery guarantees across channels, building a fast full-text search index over billions of messages, and managing the complex permission model of workspaces, channels, and threads.

WebSocketSearchWorkspace
Slack ·Microsoft ·Meta
100K reads/s100ms p99
Open
Hard

Metrics / Monitoring System

Design a metrics collection and monitoring system like Datadog, Prometheus, or New Relic. The system ingests millions of time-series data points per second from thousands of servers, stores them efficiently with configurable retention, supports real-time dashboarding, and triggers alerts based on complex threshold and anomaly detection rules. Datadog ingests trillions of data points daily — the core challenges are designing a storage engine optimized for time-series write patterns, supporting flexible aggregation queries at sub-second speed, and building a reliable alerting pipeline with low false-positive rates.

TimeSeriesAlertingAggregation
Google ·Amazon ·Stripe
100K reads/s100ms p99
Open
Hard

Netflix / Video Streaming Platform

Design a video streaming platform like Netflix that serves personalized content to 325 million subscribers across 190+ countries. Netflix accounts for over 15% of global internet bandwidth during peak hours — the key challenges are building a content recommendation engine that drives 80% of watch time, implementing adaptive bitrate streaming (ABR) that adjusts quality frame-by-frame based on network conditions, and leveraging a global CDN (Open Connect) with ISP-embedded appliances to serve 17,000+ titles with sub-second start times.

StreamingCDNRecommendations
Netflix ·Amazon ·Google
300K reads/s100ms p99
Open
Medium

Tinder / Dating App

Design a location-based dating application like Tinder that matches users based on geographic proximity, preferences, and compatibility signals. Tinder processes over 2 billion swipes per day with 75 million monthly active users — the key challenges are building an efficient geospatial index for proximity matching, a recommendation engine that surfaces relevant profiles while avoiding already-seen users, and handling the high write throughput of swipe events with real-time match notifications when two users swipe right on each other.

Geo-spatialMatchingRecommendations
Meta ·Google
100K reads/s200ms p99
Open
Hard

Google Maps / Navigation

Design a mapping and navigation platform like Google Maps that serves map tiles, computes optimal routes, provides real-time traffic updates, and estimates accurate ETAs. Google Maps serves over 1 billion daily active users and processes 1 billion kilometers of driving directions daily — the core challenges are serving pre-rendered map tiles at multiple zoom levels from a multi-petabyte tile corpus, computing shortest paths on a road graph with hundreds of millions of edges using hierarchical algorithms (Contraction Hierarchies / A*), and ingesting real-time GPS probe data from millions of devices to update traffic conditions every 30 seconds.

Geo-spatialGraphReal-time
Google ·Uber ·Airbnb
500K reads/s200ms p99
Open
Hard

Zoom / Video Conferencing

Design a real-time video conferencing platform like Zoom that supports meetings with up to 1000 participants, screen sharing, recording, and breakout rooms. Zoom handles over 300 million daily meeting participants with end-to-end latency under 150ms — the core challenges are building a Selective Forwarding Unit (SFU) architecture that routes video streams without transcoding to minimize latency, managing bandwidth allocation when dozens of participants have cameras enabled simultaneously, and providing reliable recording with server-side mixing for cloud playback.

WebRTCReal-timeMedia
Microsoft ·Google ·Meta
50K reads/s50ms p99
Open
Hard

Doordash / Food Delivery

Design a food delivery platform like DoorDash or Uber Eats that connects customers, restaurants, and delivery drivers in real-time. DoorDash processes over 750 million orders per quarter across 500,000+ merchant partners — the core challenges are building a real-time dispatch system that optimally matches orders to drivers (considering location, capacity, and estimated completion times), maintaining accurate ETAs that update as conditions change, and handling the three-sided marketplace where restaurant prep times, driver routes, and customer expectations must all be balanced simultaneously.

Geo-spatialReal-timeDispatch
Uber ·Amazon ·Google
80K reads/s200ms p99
Open
Medium

Reddit / Social News

Design a social news aggregation and discussion platform like Reddit. Users submit posts to topic-based communities (subreddits), vote content up or down, and engage in deeply nested comment threads. Reddit serves 97+ million daily active users across 100,000+ active communities — the key challenges are implementing a ranking algorithm (hot, top, controversial, best) that surfaces quality content across communities of vastly different sizes, efficiently storing and rendering deeply nested comment trees with thousands of replies, and building a moderation system that scales across volunteer moderators.

RankingCommentsVoting
Meta ·Google
200K reads/s200ms p99
Open
Hard

Airbnb / Booking Platform

Design a property rental and booking platform like Airbnb that connects hosts with guests for short-term stays. Airbnb has 7+ million active listings across 220 countries with billions of monthly searches — the core challenges are building a search system that handles complex multi-dimensional queries (location, dates, price, amenities, guest count), implementing a booking and reservation system that prevents double-booking across overlapping date ranges, and building a dynamic pricing algorithm that helps hosts optimize revenue based on seasonality, local events, and comparable listings.

SearchBookingGeo-spatial
Airbnb ·Amazon ·Google
100K reads/s200ms p99
Open
Hard

WhatsApp / Messaging

Design an end-to-end encrypted messaging platform like WhatsApp that handles 100+ billion messages per day across 3 billion monthly active users. The server never sees plaintext message content — the core challenges are implementing the Signal Protocol for end-to-end encryption with perfect forward secrecy, reliably delivering messages to offline users (store-and-forward), efficiently fanning out messages in group chats (up to 1024 members), and synchronizing message state across multiple linked devices while maintaining encryption guarantees.

EncryptionWebSocketMessaging
Meta ·Google
100K reads/s50ms p99
Open
Hard

Google Search / Search Engine

Design a web search engine like Google that crawls billions of web pages, builds an inverted index, ranks results by relevance, and returns the top results in under 200ms. Google processes over 8.5 billion searches per day across an index of hundreds of billions of pages (hundreds of petabytes) — the core challenges are building and maintaining a distributed inverted index that maps every word to the documents containing it, implementing a ranking algorithm (PageRank + hundreds of signals) that surfaces the most relevant results, and serving queries with sub-200ms latency by scattering the query across thousands of index shards in parallel.

SearchIndexingPageRank
Google ·Microsoft ·Amazon
500K reads/s200ms p99
Open
Medium

Yelp / Location-Based Service

Design a location-based business discovery and review platform like Yelp or Google Places. Users search for businesses by category and proximity, browse photos and reviews, and contribute their own ratings. Yelp indexes over 330 million reviews for 7+ million businesses — the core challenges are building an efficient geospatial index (QuadTree or Geohash) that supports proximity search with category filters, aggregating review scores in real-time as new reviews come in, and serving business detail pages with rich media from a global CDN.

Geo-spatialSearchReviews
Google ·Uber ·Airbnb
100K reads/s200ms p99
Open
Hard

TikTok / Short Video

Design a short-form video platform like TikTok that serves personalized video feeds to over 1.5 billion monthly active users. TikTok's recommendation engine is its core competitive advantage — it builds interest graphs from watch-time signals (not just social graphs) to surface relevant content even for new users within minutes. The platform processes billions of video views per day with a multi-petabyte content library — the key challenges are building the For You Page (FYP) recommendation algorithm, a high-throughput video transcoding pipeline that processes millions of uploads daily, and a content moderation system that reviews content before publication.

RecommendationsCDNStreaming
Meta ·Google ·TikTok
500K reads/s100ms p99
Open
Hard

Distributed Message Queue (Kafka)

Design a distributed message queue system like Apache Kafka that provides durable, ordered, and high-throughput message delivery between services. Kafka processes trillions of messages per day at companies like LinkedIn, handling 1M+ messages/second per broker — the core challenges are designing a partitioned commit log that supports parallel consumption, implementing consumer group coordination with partition rebalancing, achieving exactly-once semantics through idempotent producers and transactional writes, and maintaining data durability through in-sync replica (ISR) sets with configurable acknowledgment levels.

QueueDistributedReplication
LinkedIn ·Amazon ·Microsoft
1M reads/s5ms p99
Open
Hard

Digital Wallet / UPI

Design a digital wallet and P2P payment system like Google Pay, PayTM, or UPI (Unified Payments Interface). India's UPI network processes over 16 billion transactions per month across 600+ banks — the core challenges are maintaining strict financial consistency with double-entry bookkeeping, achieving exactly-once transaction execution through idempotency keys (critical when network timeouts cause retries), implementing distributed locks for concurrent balance updates, and meeting regulatory requirements for transaction audit trails, KYC compliance, and settlement reconciliation with banking partners.

ACIDIdempotentLedger
Stripe ·PayPal ·Google
50K reads/s200ms p99
Open
Medium

Online Code Editor

Design an online code editor and execution platform like Replit, CodeSandbox, or VS Code for the Web. The system supports real-time collaborative editing, sandboxed code execution in 50+ programming languages, and a virtual file system per project. Replit serves 20+ million developers — the core challenges are implementing real-time collaboration with conflict resolution (OT/CRDT) across multiple cursors, securely sandboxing user code execution in isolated containers with resource limits (CPU, memory, network), and providing Language Server Protocol (LSP) features (autocomplete, go-to-definition, error diagnostics) with low latency.

CollaborationSandboxWebSocket
GitHub ·Google ·Microsoft
30K reads/s100ms p99
Open
Medium

CI/CD Pipeline

Design a continuous integration and continuous deployment platform like GitHub Actions, GitLab CI, or Jenkins. The system orchestrates build pipelines triggered by code commits, runs tests in parallel across isolated environments, stores build artifacts, and deploys to production using strategies like blue-green or canary. GitHub Actions processes millions of workflow runs daily — the core challenges are efficiently scheduling and executing build jobs across a fleet of heterogeneous runners, managing artifact storage and caching for fast builds, and implementing reliable deployment orchestration with automatic rollback on failure detection.

PipelineDeploymentOrchestration
GitHub ·Google ·Microsoft
20K reads/s500ms p99
Open

Each problem loads requirements, hints, and constraints directly in the studio.

Rubric

Structured feedback, not vibes

Five dimensions, numeric scores, and verdict bands — the same report you get after Evaluate in the studio.

Overall score

82/ 100
Good — approaching Architect

Same rubric engine as the studio — run simulation, then evaluate your diagram.

Verdict bands

Needs workDevelopingGoodStrongArchitect

Five-axis breakdown

What Staff+ panels actually grade on.

  • Scalability88

    Horizontal scale & bottlenecks

  • Availability74

    Fault tolerance & replication

  • Latency91

    P99 paths & caching

  • Cost65

    Infra spend vs requirements

  • Trade-offs82

    CAP, consistency, patterns

86+ hits Architect band in the studio.

Run simulation

Pricing

Free & open source

No subscription. No credit card. Clone the repo and run the full studio locally.

Forever freeOpen source · self-host

Open Studio plan

0

per month · per engineer · forever

Full design canvas

30 production-grade components

Traffic simulation

Watch load flow through your diagram

Interview mode

45-min phased timers

AI architect

Optional — your Gemini key

  • 35 system design problems
  • AI scoring across 5 areas
  • Fork, extend & self-host
  • No signup for local use
Open StudioView on GitHub

Paid interview prep tools often run ₹500–2,000/mo. SysDes is ₹0 because it's open source.

FAQ

Questions before you start

Everything you need to know about running SysDes locally.

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