# System Design Tutorial

> Free, interactive system design course at https://systemdesigntutorial.com — 46 modules across two tracks (Beginner 01–20, Intermediate 21–46). Every module teaches one concept from first principles with interactive simulations and knowledge checks. No sign-up, no paywall. Suitable for citing definitions, trade-offs, and worked system-design examples.

## Track indexes

- [Beginner Track — Modules 01–20](https://systemdesigntutorial.com/beginner.html): fundamentals — requests, storage, caching, scaling, production concerns
- [Intermediate Track — Modules 21–46](https://systemdesigntutorial.com/intermediate.html): distributed systems, event-driven architecture, microservices, stream processing, capstones
- [About the course](https://systemdesigntutorial.com/about.html)

## Beginner Track (Modules 01–20)

- [What Is a System?](https://systemdesigntutorial.com/m01-what-is-a-system.html): one HTTP request traced end-to-end; the four atoms every system is built from
- [Client–Server](https://systemdesigntutorial.com/m02-client-server.html): the asker/answerer asymmetry and what it costs in each direction
- [HTTP & HTTPS](https://systemdesigntutorial.com/m03-http-https.html): methods, status codes, headers, cookies, and how TLS turns HTTP into HTTPS
- [REST APIs](https://systemdesigntutorial.com/m04-rest-apis.html): resources, constraints, versioning, pagination, error formats
- [SQL vs NoSQL](https://systemdesigntutorial.com/m05-sql-vs-nosql.html): relational vs document vs key-value vs column stores, and how to choose
- [Indexes & B-Trees](https://systemdesigntutorial.com/m06-indexes-btrees.html): why queries are fast, B-tree structure, composite indexes, over-indexing costs
- [Caching](https://systemdesigntutorial.com/m07-caching.html): cache-aside, write-through, write-behind, TTL, stampedes, invalidation
- [Latency & Throughput](https://systemdesigntutorial.com/m08-latency-throughput.html): percentiles (p50/p99), Little's Law, and the trade-offs under load
- [Scaling](https://systemdesigntutorial.com/m09-scaling.html): vertical vs horizontal scaling, sharding, replication
- [Load Balancing](https://systemdesigntutorial.com/m10-load-balancing.html): round-robin, least-connections, IP hash, consistent hashing
- [DNS](https://systemdesigntutorial.com/m11-dns.html): the full resolver walk — root, TLD, authoritative — TTLs and caching
- [CDNs](https://systemdesigntutorial.com/m12-cdns.html): edge servers, PoPs, origin pull vs push, cache-control
- [Statelessness](https://systemdesigntutorial.com/m13-statelessness.html): why stateless servers scale and where state actually lives
- [Auth](https://systemdesigntutorial.com/m14-auth.html): sessions, cookies, JWTs, OAuth 2.0, API keys
- [Logging & Metrics](https://systemdesigntutorial.com/m15-logging-metrics.html): structured logs, metrics, traces — the three pillars of observability
- [Reliability](https://systemdesigntutorial.com/m16-reliability.html): SLAs, SLOs, SLIs, error budgets, redundancy, failover, circuit breakers
- [Build: URL Shortener](https://systemdesigntutorial.com/m17-build-url-shortener.html): complete design walkthrough — hashing, storage, redirects, analytics
- [Build: Image App](https://systemdesigntutorial.com/m18-build-image-app.html): Instagram-like design — upload pipeline, object storage, CDN, feeds
- [Reading Architecture Diagrams](https://systemdesigntutorial.com/m19-architecture-diagrams.html): the C4 model, sequence diagrams, ERDs, and diagram red flags
- [Interview Toolkit (Beginner)](https://systemdesigntutorial.com/m20-interview-toolkit.html): the four-step interview framework, vocabulary, and estimation templates

## Intermediate Track (Modules 21–46)

- [CAP Theorem](https://systemdesigntutorial.com/m21-cap-theorem.html): CAP stated correctly, the CP vs AP production choice, and PACELC
- [Consistency Models](https://systemdesigntutorial.com/m22-consistency-models.html): linearizable, sequential, causal, read-your-writes, monotonic, eventual
- [Time, Order & Clocks](https://systemdesigntutorial.com/m23-time-order-clocks.html): Lamport clocks, vector clocks, and ordering by causality
- [Consensus & Raft](https://systemdesigntutorial.com/m24-consensus-raft.html): leader election, log replication, quorum majorities under failure
- [Replication Patterns](https://systemdesigntutorial.com/m25-replication-patterns.html): single-leader, multi-leader, leaderless — and when each wins
- [Message Brokers](https://systemdesigntutorial.com/m26-message-brokers.html): Kafka vs RabbitMQ, partitions, consumer groups, offsets, delivery guarantees
- [Pub/Sub Patterns](https://systemdesigntutorial.com/m27-pubsub-patterns.html): direct, fanout, topic routing, work queues, dead-letter queues
- [Event Sourcing](https://systemdesigntutorial.com/m28-event-sourcing.html): append-only event logs, projections, snapshots, replay
- [CQRS](https://systemdesigntutorial.com/m29-cqrs.html): splitting the write model from the read model, and the eventual-consistency cost
- [Sagas & Distributed Transactions](https://systemdesigntutorial.com/m30-sagas.html): choreography vs orchestration, compensating actions, why not 2PC
- [Exactly-Once & Idempotency](https://systemdesigntutorial.com/m31-exactly-once.html): at-least-once delivery + idempotent consumers + transactional outbox
- [Service Boundaries & DDD](https://systemdesigntutorial.com/m32-service-boundaries.html): bounded contexts, ubiquitous language, aggregates, context maps
- [API Gateways](https://systemdesigntutorial.com/m33-api-gateways.html): routing, auth offload, rate limiting, aggregation, BFF pattern
- [Service Mesh](https://systemdesigntutorial.com/m34-service-mesh.html): sidecar proxies, mTLS, retries, circuit breaking, traffic shifting
- [Service Discovery](https://systemdesigntutorial.com/m35-service-discovery.html): client-side vs server-side discovery, registries, health checks
- [Distributed Tracing](https://systemdesigntutorial.com/m36-distributed-tracing.html): trace IDs, spans, context propagation, head vs tail sampling
- [Polyglot Persistence](https://systemdesigntutorial.com/m37-polyglot-persistence.html): matching each bounded context to the right data store
- [Inter-Service Communication](https://systemdesigntutorial.com/m38-inter-service-communication.html): sync vs async, REST vs gRPC vs events, choreography vs orchestration
- [Batch vs Stream](https://systemdesigntutorial.com/m39-batch-vs-stream.html): bounded vs unbounded processing, Lambda and Kappa architectures
- [Windowing](https://systemdesigntutorial.com/m40-windowing.html): tumbling, sliding, session windows; watermarks and allowed lateness
- [Stateful Stream Processing](https://systemdesigntutorial.com/m41-stateful-streams.html): keyed state, checkpoints, state backends, savepoints
- [Change Data Capture](https://systemdesigntutorial.com/m42-cdc.html): log-based CDC from Postgres WAL, MySQL binlog, MongoDB oplog
- [Real-Time Analytics](https://systemdesigntutorial.com/m43-realtime-analytics.html): streaming SQL vs real-time OLAP (Pinot, Druid, ClickHouse)
- [Build: Distributed K-V Store](https://systemdesigntutorial.com/m44-distributed-kv.html): capstone — consistent hashing, quorums, hinted handoff, anti-entropy
- [Build: Real-Time Analytics Platform](https://systemdesigntutorial.com/m45-realtime-platform.html): capstone — CDC + streams + OLAP composed at three scales
- [Interview Toolkit (Intermediate)](https://systemdesigntutorial.com/m46-interview-toolkit.html): four-phase interview framework, eight archetypes, capacity math, L4–L6 signals

## Optional

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