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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

Ranked by how often each question comes up in real interviews. #1 is the most common.

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🔒