Level 9: Microservices

Lessons in level 9

1. Why Microservices Exist — and When Not to Use Them — Independent deployability is the point; complexity is the price.
2. Finding Service Boundaries & Splitting the Monolith — Information hiding, bounded contexts and the strangler fig.
3. Database per Service & Data Ownership — Why sharing a database couples services, and how to live without joins.
4. Synchronous vs Asynchronous Communication — REST, gRPC and events — temporal coupling and its consequences.
5. API Gateways, BFFs & Service Discovery — How clients find services, and what belongs at the edge.
6. Timeouts, Retries & Retry Storms — Why naive retries turn a slow service into an outage.
7. Circuit Breakers & Bulkheads — Fail fast, isolate damage, and recover gracefully.
8. Idempotency: Making Retries Safe — Idempotency keys, deduplication and the myth of exactly-once.
9. Distributed Transactions: 2PC, Sagas & the Outbox — Keep data consistent across services without a global transaction.
10. Observability: Logs, Metrics, Traces & SLOs — Answer “why is checkout slow?” across ten services.
11. Deployment: Containers, Kubernetes, Canary & Feature Flags — Ship small, ship often, and limit the blast radius.
12. Testing Microservices & Consumer-Driven Contracts — Catch breaking API changes without a giant end-to-end suite.
13. Teams, Ownership & Conway’s Law — Architecture and org charts shape each other.

Source books

• Building Microservices — Sam Newman
• DDD — Eric Evans
• Software Architecture — Mark Richards, Neal Ford, Pramod Sadalage, Zhamak Dehghani
• DDIA — Martin Kleppmann

Other levels

• Previous level 8: Data-Intensive Systems
• Next level 10: Architecture That Survives Change
• All levels