# System Design > Architecture-level thinking: low-level design, scalability, distributed systems, event-driven design, and end-to-end case studies. Canonical: https://learn.significanthobbies.com/curriculum/tracks/system-design Architecture-level thinking: low-level design, scalability, distributed systems, event-driven design, and end-to-end case studies. This track contains 26 connected concepts. Mastery means explaining each mechanism, predicting its failure modes, and supporting decisions with code, measurements, or a reviewable design artifact. ## Roadmaps - [12-Month Advanced AI Infrastructure](https://learn.significanthobbies.com/curriculum/roadmaps/ai-infra-12-month) — Reach the depth to design and reason about systems like Turbopuffer, and ship them through HighSignal and Codevetter. - [Disk-First Databases & RAM](https://learn.significanthobbies.com/curriculum/roadmaps/db-disk-first) — Build a mechanism-first mental model of how disk-based DBs spend RAM, and why. - [Runtime — what every runtime has to do](https://learn.significanthobbies.com/curriculum/roadmaps/runtime) — Build one cross-cutting mental model for V8, JVM, Go, BEAM, .NET CLR, vLLM, SGLang, Cloudflare Workers, and wasmtime. - [The Software Engineering Landscape (2026)](https://learn.significanthobbies.com/curriculum/roadmaps/swe-landscape) — Get a working mental model of every major systems-software domain — LLMs, DBs, streaming, game engines, containers, browsers, compilers, OS, networking, distributed, build, crypto. - [LLD Practice](https://learn.significanthobbies.com/curriculum/roadmaps/lld-practice) — Build the design-rounds muscle: model state and behaviour explicitly, justify every class boundary. - [HLD Practice](https://learn.significanthobbies.com/curriculum/roadmaps/hld-practice) — Be able to design X — feed, chat, ride-hailing, search — under a 45-minute clock with credible numbers. ## Concepts - [Object Modeling](https://learn.significanthobbies.com/curriculum/concepts/object-modeling) (core) — Identifying classes, attributes, relationships. - [State Machines](https://learn.significanthobbies.com/curriculum/concepts/state-management) (core) — States, transitions, guards. - [Strategy Pattern](https://learn.significanthobbies.com/curriculum/concepts/strategy-pattern) (core) — Interchangeable algorithms. - [Observer Pattern](https://learn.significanthobbies.com/curriculum/concepts/observer-pattern) (core) — Pub/sub, event propagation. - [Factory & Creational](https://learn.significanthobbies.com/curriculum/concepts/factory-creational) (core) — Abstract factory, builder, singleton. - [Decorator & Structural](https://learn.significanthobbies.com/curriculum/concepts/decorator-structural) (core) — Decorator, adapter, composite. - [Concurrency Design](https://learn.significanthobbies.com/curriculum/concepts/concurrency-design) (advanced) — Thread-safety, locks, producer-consumer. - [Command & Chain](https://learn.significanthobbies.com/curriculum/concepts/command-chain) (core) — Command, undo, chain of responsibility. - [Booking & Inventory](https://learn.significanthobbies.com/curriculum/concepts/booking-inventory) (advanced) — Reservation, hold-confirm, optimistic locking. - [Game/Simulation Design](https://learn.significanthobbies.com/curriculum/concepts/game-design) (core) — Turn engines, board state, rules. - [Load Balancing](https://learn.significanthobbies.com/curriculum/concepts/load-balancing) (core) — L4/L7, consistent hashing, health checks. - [Consistent Hashing](https://learn.significanthobbies.com/curriculum/concepts/consistent-hashing) (advanced) — Ring, virtual nodes, rebalancing. - [Consensus](https://learn.significanthobbies.com/curriculum/concepts/consensus) (advanced) — Raft, Paxos, leader election. - [Distributed Infra](https://learn.significanthobbies.com/curriculum/concepts/distributed-infra) (advanced) — Service discovery, orchestration. - [Real-time Systems](https://learn.significanthobbies.com/curriculum/concepts/messaging-realtime) (core) — WebSockets, server-sent events, presence, synchronization, ordering, reconnects, optimistic UI, and conflict handling. - [Feed Systems](https://learn.significanthobbies.com/curriculum/concepts/social-media) (core) — Fan-out write/read, timeline. - [Streaming Media](https://learn.significanthobbies.com/curriculum/concepts/streaming-media) (core) — CDN, HLS, transcoding pipeline. - [Geo Systems](https://learn.significanthobbies.com/curriculum/concepts/location-transport) (core) — Geohash, quadtree, dispatch. - [Collaboration Systems](https://learn.significanthobbies.com/curriculum/concepts/collaboration-productivity) (advanced) — Causality, OT, CRDT merge laws, and offline conflict resolution. - [Search Platform Design](https://learn.significanthobbies.com/curriculum/concepts/search-platform-design) (advanced) — End-to-end design of a search platform: ingestion, indexing, query, ranking. - [RAG System Design](https://learn.significanthobbies.com/curriculum/concepts/rag-system-design) (advanced) — Architecting a production RAG system: ingestion, retrieval, generation, evals. - [Capacity Estimation](https://learn.significanthobbies.com/curriculum/concepts/capacity-estimation) (core) — Back-of-the-envelope QPS, storage, and bandwidth maths that sizes a design before you draw it. - [Requirements Scoping](https://learn.significanthobbies.com/curriculum/concepts/requirements-scoping) (core) — Separating functional from non-functional requirements and cutting scope to something buildable. - [Rate Limiter Design](https://learn.significanthobbies.com/curriculum/concepts/rate-limiter-design) (core) — Token bucket versus sliding window, and making a limiter work across many nodes. - [Unique ID Generation](https://learn.significanthobbies.com/curriculum/concepts/unique-id-generation) (core) — Snowflake, ULID, and UUIDv7 — unique ids without a central allocator. - [CDN & Edge Delivery](https://learn.significanthobbies.com/curriculum/concepts/cdn-edge-delivery) (core) — Cache hierarchy, origin shield, and invalidation versus TTL at the edge.