System Design Interview Simulation
Practice architecture the way interviews actually run. Choose a scenario, place components and wire the data flow, then get structured feedback.
42 scenarios
Scenarios
42/42- 01Basic System ComponentEasy
01Design a URL Shortening Service like Bitly
FreeBasic System Component · Easy - 02Collaborative SystemEasy
02Design a Task Management Application
FreeCollaborative System · Easy - 03Messaging & RealtimeMedium
03Design a Real-Time Notification System
FreeMessaging & Realtime · Medium - 04Basic System ComponentMedium
04Design a Rate Limiter
PremiumBasic System Component · Medium - 05Scheduling ServiceMedium
05Design a Distributed Job Scheduler
PremiumScheduling Service · Medium - 06Distributed ArchitectureHard
06Design a Live Streaming Platform
PremiumDistributed Architecture · Hard - 07Collaborative SystemHard
07Design a File Storage Service like Dropbox
PremiumCollaborative System · Hard - 08Basic System ComponentEasy
08Design a Load Balancer for Web Servers
PremiumBasic System Component · Easy - 09Basic System ComponentMedium
09Design a Distributed ID Generator
PremiumBasic System Component · Medium - 10Proximity / TrieMedium
10Design a Search Autocomplete System
PremiumProximity / Trie · Medium - 11Basic System ComponentHard
11Design a Key-Value Store like Redis or DynamoDB
PremiumBasic System Component · Hard - 12Proximity / TrieHard
12Design a Ride-Sharing Service like Uber or Lyft
PremiumProximity / Trie · Hard - 13Basic System ComponentEasy
13Design a Pastebin
PremiumBasic System Component · Easy - 14Scheduling / CrawlMedium
14Design a Web Crawler
PremiumScheduling / Crawl · Medium - 15Messaging & RealtimeHard
15Design a Chat / Messaging System like WhatsApp
PremiumMessaging & Realtime · Hard - 16Social / FeedHard
16Design a News Feed like Twitter or Facebook
PremiumSocial / Feed · Hard - 17Distributed ArchitectureHard
17Design a Video-on-Demand Platform like YouTube or Netflix
PremiumDistributed Architecture · Hard - 18Basic System ComponentMedium
18Design a Gaming Leaderboard
PremiumBasic System Component · Medium - 19Messaging & AsyncMedium
19Design an Email / Notification Delivery Service
PremiumMessaging & Async · Medium - 20E-Commerce / InventoryHard
20Design a Ticket Booking System like Ticketmaster
PremiumE-Commerce / Inventory · Hard - 21Social / MediaHard
21Design a Photo Sharing App like Instagram
PremiumSocial / Media · Hard - 22Collaborative SystemHard
22Design a Collaborative Document Editor like Google Docs
PremiumCollaborative System · Hard - 23Basic System ComponentEasy
23Design a Content Delivery Network (CDN)
PremiumBasic System Component · Easy - 24Proximity / LocationMedium
24Design a Proximity Service like Yelp or Nearby Places
PremiumProximity / Location · Medium - 25ObservabilityMedium
25Design a Distributed Logging System
PremiumObservability · Medium - 26FintechHard
26Design a Payment System
PremiumFintech · Hard - 27E-Commerce / RealtimeHard
27Design an Online Auction System like eBay
PremiumE-Commerce / Realtime · Hard - 28Basic System ComponentEasy
28Design a Distributed Session Store
PremiumBasic System Component · Easy - 29Messaging & AsyncMedium
29Design a Reliable Webhook Delivery System
PremiumMessaging & Async · Medium - 30ObservabilityMedium
30Design a Metrics / Monitoring System
PremiumObservability · Medium - 31Proximity / MarketplaceHard
31Design a Food Delivery Service like DoorDash or Uber Eats
PremiumProximity / Marketplace · Hard - 32Distributed ArchitectureHard
32Design a Music Streaming Service like Spotify
PremiumDistributed Architecture · Hard - 33Basic System ComponentHard
33Design a Distributed Lock Service
PremiumBasic System Component · Hard - 34E-Commerce / InventoryHard
34Design a Hotel Booking System like Booking.com
PremiumE-Commerce / Inventory · Hard - 35Analytics / AdsHard
35Design an Ad Click Aggregator
PremiumAnalytics / Ads · Hard - 36ML / PersonalizationHard
36Design a Recommendation System
PremiumML / Personalization · Hard - 37Messaging & RealtimeHard
37Design a Video Conferencing System like Zoom
PremiumMessaging & Realtime · Hard - 38Basic System ComponentEasy
38Design a DNS System
PremiumBasic System Component · Easy - 39Collaborative SystemMedium
39Design a Calendar System like Google Calendar
PremiumCollaborative System · Medium - 40Scheduling / ComputeHard
40Design an Online Judge like LeetCode
PremiumScheduling / Compute · Hard - 41E-CommerceHard
41Design an E-Commerce Platform like Amazon
PremiumE-Commerce · Hard - 42Social / MediaHard
42Design a Short-Video Platform like TikTok
PremiumSocial / Media · Hard
System design interview guide
Practise the decisions behind the diagram, not just the boxes
There is rarely one correct architecture in a system design interview. The interviewer is watching how you clarify an ambiguous brief, make the request flow concrete, and choose trade-offs when scale or failure changes the problem.
A useful interview sequence
- 1. Clarify the user, the success metric, and the constraints that actually matter.
- 2. Draw the request path; make data ownership and asynchronous work explicit.
- 3. Defend the trade-off you chose under scale, latency, and partial failure.
Start with a free scenario
Read the brief, make your assumptions, connect the architecture on the canvas, then see which decisions the review found missing.