🏛️ System Design Roadmap: core → advanced
Level 1: Fundamentals (Phases 1–2)
- Client–server, HTTP, REST, stateless services
- Vertical vs horizontal scaling; load balancers
- SQL vs NoSQL; indexes; replication basics
- Caching layers (browser, CDN, app, DB); cache-aside
- Estimation Cheatsheet
Level 2: Building blocks (Phases 2–3) → Building Blocks
- Load balancer, API gateway, reverse proxy
- Cache (Redis), CDN, object storage (S3)
- Message queue vs event log (SQS/RabbitMQ vs Kafka)
- Search index, rate limiter, ID generator, distributed lock
- Blob + metadata split; presigned URLs
Level 3: Distributed systems (Phase 3) → Distributed Systems
- Replication, partitioning/sharding, consistent hashing
- Consistency models, CAP/PACELC, quorums
- Consensus (Raft), leader election, clocks
- Idempotency, exactly-once illusions, ordering
Level 4: Architecture patterns (Phase 3) → Architecture Patterns
- Monolith → modular monolith → microservices
- Event-driven, CQRS, event sourcing, saga, outbox
- DDD strategic design (bounded contexts, context maps)
- Hexagonal / clean architecture (inside a service)
- Resilience: timeouts, retries, circuit breakers, bulkheads, load shedding
Level 5: Production & scale (Phases 4–6)
- Multi-region, active-active vs active-passive, cell-based architecture
- Observability, SLOs, capacity planning
- Zero-downtime deployments, schema migrations (expand/contract), feature flags
- Cost-aware architecture
- AI systems architecture (RAG, agents, LLM gateways) → AI Engineering Roadmap
🎤 Interview framework (45–60 min)
| Step | Time | Output |
|---|---|---|
| 1. Requirements | 5 min | Functional (3–5 core features), non-functional (scale, latency, availability, consistency) |
| 2. Estimates | 3 min | QPS (avg/peak), storage/yr, bandwidth; only estimate what drives decisions |
| 3. API | 5 min | Key endpoints/events |
| 4. Data model | 5 min | Entities, keys, access patterns → DB choice |
| 5. High-level design | 10 min | Boxes and arrows covering every functional requirement |
| 6. Deep dives | 15 min | The 2–3 hardest parts (contention, hot keys, fan-out, consistency) |
| 7. Wrap-up | 5 min | Bottlenecks, failure modes, monitoring, evolution |
What interviewers score
Structured approach · clear trade-offs · depth in 1–2 areas · handling of failures · communication. Not the number of boxes.
Resources
- ⭐ DDIA · System Design Interview Vol 1 & 2 (Xu) · Understanding Distributed Systems (Vitillo)
- ⭐ Hello Interview (written deep dives + guided practice) · ByteByteGo · system-design-primer (GitHub)
- YouTube: Jordan Has No Life, Hello Interview, ByteByteGo, Gaurav Sen (intro)
- Real architectures: Engineering Blogs & Papers
- Practice: Case Studies (use the System Design Case template)