System Design Cheat Sheet (2026)

: Justify decisions, such as sacrificing consistency for higher availability. Medium +6 Common Design Patterns & Templates Modern cheat sheets often include templates for specific real-world applications to help engineers recognize recurring problems: LockedIn AI +1 System Type Key Components/Challenges Recommended Cheat Sheet Solution URL Shortener Collision risk, high read traffic Base62 encoding, LRU caching Messaging App Real-time delivery, message order WebSockets, Kafka message queues News Feed Large-scale data, personalization Hybrid push/pull models, fan-out Video Streaming Large file handling, latency CDNs, Adaptive Bitrate Streaming Popular Resources Several industry-standard cheat sheets are widely referenced: ByteByteGo System Design Cheat Sheet : Focuses on high-level availability and throughput solutions. GitHub - System Design Primer : A massive repository of patterns and interview questions. Grokking Modern System Design

| Problem | Key pattern | |---------|--------------| | URL shortener | Base62 encoding, write-heavy DB, cache for redirects | | Chat system | WebSocket + message queue, offline storage, presence tracking | | Social feed | Fanout on write (for small audiences) / read (for large) | | Rate limiter | Token bucket / sliding window (in-memory + Redis) | | Distributed ID generator | Snowflake, UUIDv7, DB sequence with segments | | Payment system | Idempotency keys, 2PC / Saga, idempotent consumers | | Leaderboard | Redis sorted sets, sharded with approximate ranking | system design cheat sheet

Start with relational. Scale with read replicas → cache → sharding → NoSQL when needed. : Justify decisions, such as sacrificing consistency for