System Design Interview
Interactive Practice Problems
Master the most common system design interview questions with interactive visualizations. Each problem includes capacity estimation calculators, architecture diagrams, and algorithm simulators to help you build real intuition — not just memorize answers.
URL Shortener
Base62 encoding, capacity estimation, hash vs counter ID generation, and caching strategies
Rate Limiter
Token bucket, sliding window, fixed window, and leaky bucket algorithms with interactive simulators
Chat System
WebSocket vs polling, message ordering, presence detection, and fan-out strategies
Distributed Cache
Consistent hashing, write-through/write-behind strategies, LRU/LFU eviction, and cache-aside pattern
Web Crawler
URL frontier, politeness policies, deduplication, and distributed crawling architecture
Key-Value Store
Partitioning, replication, consistency models, and conflict resolution strategies
Notification System
Push vs pull delivery, priority queues, rate limiting, and multi-channel routing
Payment System
Idempotency keys, transaction flows, retry logic, reconciliation, and double-entry ledger
Search Autocomplete
Trie data structure, top-K ranking, latency optimization, and frequency aggregation
Video Streaming
Bitrate encoding, CDN routing, adaptive streaming (HLS/DASH), and capacity planning
Ticket Booking System
Seat selection, double-booking prevention, optimistic vs pessimistic locking, and queue-based checkout
Ride Sharing
Geospatial matching, surge pricing, trip lifecycle state machine, and ETA calculation
Social Media Feed
Fan-out on write vs read, feed ranking, celebrity problem, and hybrid delivery strategies
File Storage
Chunking, deduplication, metadata DB, sync conflict resolution, and content-addressable storage
Real-Time Collaboration
OT vs CRDT, cursor presence, version history, and low-latency document synchronization
Metrics & Monitoring
Time-series DB, push vs pull ingestion, aggregation pipelines, and alerting design
E-Commerce Platform
Catalog service, cart, checkout, inventory management with optimistic locking, and payment processing
Social Graph
Graph DB vs relational, friend-of-friend recommendations, feed fanout, and graph partitioning
Leaderboard
Redis sorted sets, skip list traversal, sharding strategies, and real-time vs near-real-time ranking
Distributed Job Scheduler
Priority queues, worker pool scaling, exactly-once execution, cron parsing, and failure handling
Message Queue
Kafka vs RabbitMQ vs SQS — partition routing, consumer groups, rebalancing, and capacity planning
Online Judge
Submission pipeline, sandbox isolation, test case execution, capacity planning, and plagiarism detection
Photo storage, CDN architecture, image processing pipeline, feed ranking, and stories system
Parking Lot
OOP class design, space allocation algorithms, pricing strategies, and real-time occupancy tracking
Spotify
Audio chunking, adaptive bitrate streaming, recommendation engine, playlist management, and offline sync
Aurora DSQL Storage
How S3 holds the authoritative journal and NVMe caches the hot path — the storage split that gives DSQL its multi-region, no-failover behavior