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🏗 Interview Prep

System Design

Scaling, caching, databases, queues and the classic "design X" questions, each with a diagram you can step through.

📘 Learn it from scratch

Visual, hands-on lessons for every pattern in this topic. Do the lesson, then come back and the questions click.

Scaling from 1 to 1 Million UsersCaching Strategies & Building an LRU CacheLoad BalancersDatabases at Scale: Replication & ShardingQueues & Background JobsAcing System Design Interviews (+ Rate Limiter)

100 questions, most asked first

Ordered so the most useful questions for learning each pattern come first.

Any difficulty Easy Medium Hard

All patterns Design interview Scaling basics Caching Load balancing Databases at scale Consistent hashing CAP & consistency Queues & async Rate limiting CDNs & storage Real-time Reliability

#1Design a URL shortener (like bit.ly)Design interviewMediumFree #2How do you scale a web app from 1 to 1 million users?Scaling basicsMediumFree #3Caching strategiesCachingMediumFree #4Load balancersLoad balancingMediumFree #7The CAP theoremCAP & consistencyMediumFree #8Message queues and background jobsQueues & asyncMediumFree #9Design a rate limiterRate limitingMediumFree #10Serving images and video at scaleCDNs & storageMediumFree Unlock 41 more System Design questions · all 1,200 questions for $39/year (about 11¢ a day)See full access #13Design a notification systemQueues & asyncMedium🔒#21Design a unique ID generatorDesign interviewMedium🔒#24Design a real-time leaderboardCachingMedium🔒#27What does an API gateway do?Load balancingMedium🔒#30Add full-text search to a websiteDatabases at scaleMedium🔒#31Monolith vs microservicesScaling basicsMedium🔒#32Back-of-the-envelope estimationDesign interviewMedium🔒#33Latency numbers every engineer should knowScaling basicsMedium🔒#34Availability, SLAs and the "nines"ReliabilityMedium🔒#35Circuit breakers, timeouts and retriesReliabilityMedium🔒#37Event-driven architecture and pub/subQueues & asyncMedium🔒#41Blue-green, canary and rolling deploymentsReliabilityMedium🔒#42Logs, metrics and traces (observability)ReliabilityMedium🔒#43Backups and disaster recovery (RPO and RTO)ReliabilityMedium🔒#50Edge computing and serverlessCDNs & storageMedium🔒#52Design "restaurants near me" (like Yelp)Databases at scaleMedium🔒#54Design reliable webhook deliveryQueues & asyncMedium🔒#59Design centralized loggingReliabilityMedium🔒#60Design an online learning platform (like this one)Design interviewMedium🔒#62Stateless vs stateful servicesScaling basicsMedium🔒#63Sticky sessionsLoad balancingMedium🔒#64Block vs file vs object storageCDNs & storageMedium🔒#68Cache eviction policiesCachingMedium🔒#69Security in system design interviewsReliabilityMedium🔒#70Data pipelines, warehouses and lakesDatabases at scaleMedium🔒#71Design view and like countersCachingMedium🔒#74Design a calendar with schedulingDesign interviewMedium🔒#76Design a feature flag systemReliabilityMedium🔒#77Design a content moderation pipelineQueues & asyncMedium🔒#80Design a live poll or voting systemCAP & consistencyMedium🔒#81How to run a system design interviewDesign interviewMedium🔒#83How to choose a database for a designDatabases at scaleMedium🔒#86Service discoveryLoad balancingMedium🔒#89API versioning and backward compatibilityDesign interviewMedium🔒#90Graceful degradationReliabilityMedium🔒#93AutoscalingScaling basicsMedium🔒#94Containers and Kubernetes in system designScaling basicsMedium🔒#97Design a hotel booking systemCAP & consistencyMedium🔒#98Designing for privacy (GDPR) and data deletionReliabilityMedium🔒#99Designing for costScaling basicsMedium🔒#100Walk me through the design of something you builtDesign interviewMedium🔒