System Design Patterns

**Decision framework**: - Start monolith, extract services when pain emerges (the "monolith first" approach) - Extract when: deploy cadence conflicts, scaling mismatches, team ownership boundaries - **Red flag**: Microservices adopted before product-market fit - **Red flag**: "Distributed monolith" — services tightly coupled, must deploy together - **Red flag**: Shared database across services (defeats the purpose)