DESIGN 01
Layered walkthrough
Layered walkthroughURL Shortener
TinyURL / Bit.ly — key generation, 301 vs 302, caching, analytics
THE SYSTEM DESIGN FIELD GUIDE
Complex systems.
One layer at a time.
Go beyond the boxes and arrows. Explore real-world
architectures, understand the tradeoffs, and build your intuition.
30 in-depth designs8 categoriesBuilt to understand
The design library 30
Pick a system. Follow the decisions. See the whole picture.
Foundations
START HERE4 designsThe building blocks of scalable systems.
DESIGN 02
Layered walkthrough
Layered walkthroughRate Limiter
Token bucket, sliding window, distributed rate limiting
DESIGN 03
Layered walkthrough
Layered walkthroughKey-Value Store
Distributed KV store — consistent hashing, replication, gossip
DESIGN 04
Layered walkthrough
Layered walkthroughWeb Crawler
Politeness, URL frontier, deduplication, distributed crawling
Messaging & real-time
3 designsKeep people and services connected.
DESIGN 05
Layered walkthrough
Layered walkthroughChat System
WhatsApp / Slack — WebSocket, message ordering, presence, E2E encryption
DESIGN 06
Layered walkthrough
Layered walkthroughNotification System
Push, email, SMS — priority queues, template engine, delivery tracking
DESIGN 07
Layered walkthrough
Layered walkthroughReal-Time Collaboration
Google Docs — OT/CRDT, conflict resolution, cursor sync
Content & media
3 designsDeliver great experiences at any scale.
Search & discovery
4 designsFind the right thing, at the right time.
DESIGN 11
Layered walkthrough
Layered walkthroughSearch Engine
Google — inverted index, PageRank, query processing, distributed indexing
DESIGN 12
Layered walkthrough
Layered walkthroughTypeahead & Autocomplete
Trie-based, prefix search, ranking by popularity
DESIGN 13
Layered walkthrough
Layered walkthroughProximity Service
Yelp — geospatial indexing, quadtree, geohash, nearby search
DESIGN 14
Layered walkthrough
Layered walkthroughRecommendation System
Collaborative filtering, content-based, hybrid, real-time ranking
Infrastructure & data
5 designsThe systems that other systems depend on.
DESIGN 15
Layered walkthrough
Layered walkthroughDistributed Message Queue
Kafka — append-only log, ISR, partitioning, exactly-once, consumer groups
DESIGN 16
Layered walkthrough
Layered walkthroughContent Delivery Network
CloudFront / Cloudflare — edge caching, Anycast, TLS, edge compute, DDoS
DESIGN 17
Layered walkthrough
Layered walkthroughDistributed Cache
Redis / Memcached — eviction, persistence, clustering, cache patterns
DESIGN 18
Layered walkthrough
Layered walkthroughObject Storage
S3 — erasure coding, 11 nines durability, metadata separation, GC
DESIGN 19
Layered walkthrough
Layered walkthroughDistributed Task Scheduler
Celery / Temporal — delayed tasks, cron, DAG workflows, retry, saga
Commerce & transactions
4 designsMake every transaction count.
DESIGN 20
Layered walkthrough
Layered walkthroughPayment System
Stripe — idempotency, double-entry ledger, tokenization, PCI, fraud
DESIGN 21
Layered walkthrough
Layered walkthroughE-Commerce Platform
Amazon — catalog, cart, checkout saga, inventory, search, flash sales
DESIGN 22
Layered walkthrough
Layered walkthroughTicket Booking
Ticketmaster — seat maps, hold with Redis SET NX, virtual waiting room, anti-bot
DESIGN 23
Layered walkthrough
Layered walkthroughRide Sharing
Uber / Lyft — H3 geospatial, driver matching, surge pricing, real-time tracking
Social & collaboration
3 designsBetter experiences, built together.
DESIGN 24
Layered walkthrough
Layered walkthroughSocial Graph
LinkedIn / Facebook — adjacency lists, mutual connections, PYMK, BFS, TAO
DESIGN 25
Layered walkthrough
Layered walkthroughMetrics & Monitoring
Datadog / Prometheus — TSDB, Gorilla compression, alerting, SLOs
DESIGN 26
Layered walkthrough
Layered walkthroughFile Sync
Dropbox / Google Drive — CDC chunking, delta sync, dedup, conflict resolution
AI & modern systems
4 designsDesign for the next generation of products.
DESIGN 27
Layered walkthrough
Layered walkthroughAI Inference Platform
OpenAI API / SageMaker — GPU scheduling, continuous batching, PagedAttention, LoRA
DESIGN 28
Layered walkthrough
Layered walkthroughRAG Pipeline
Retrieval-Augmented Generation — chunking, hybrid search, reranking, citations
DESIGN 29
Layered walkthrough
Layered walkthroughEvent-Driven Architecture
Event sourcing, CQRS, sagas, CDC, schema registry, dead letter queues
DESIGN 30
Layered walkthrough
Layered walkthroughMulti-Tenant SaaS Platform
Tenant isolation, noisy neighbor, tiered plans, RLS, billing metering