Microservices Architecture Blueprint for Growth-Stage Startups

Design a Microservices Architecture for:\\\\\\\\n\\\\\\\\nCompany: [NAME]\\\\\\\\nProduct type: [SaaS / Marketplace / API-first / Consumer app]\\\\\\\\nCurrent monolith: [STACK — e.g., Node.js + PostgreSQL + Redis]\\\\\\\\nCurrent volume: [REQUESTS/DAY or EVENTS/MONTH]\\\\\\\\nTeam: [NUMBER] developers in [NUMBER] squads\\\\\\\\nMain monolith bottlenecks: [EX: billing module blocks everything, 40 min deploys, can't scale image processing alone]\\\\\\\\nCurrent infrastructure: [AWS / GCP / AZURE / BARE METAL]\\\\\\\\nCurrent SLA and target: [CURRENT UPTIME → TARGET]\\\\\\\\n\\\\\\\\n## PART 1 — EVALUATION: MICROSERVICES OR NOT?\\\\\\\\n\\\\\\\\n**Criteria to justify migration:**\\\\\\\\n\\\\\\\\nCurrent monolith score:\\\\\\\\n- [ ] Team > 15 developers (+ 1 point for microservices)\\\\\\\\n- [ ] Frequent deploys blocked by unrelated parts (+1)\\\\\\\\n- [ ] Need to scale components independently (+1)\\\\\\\\n- [ ] Different squads working on the same files (+1)\\\\\\\\n- [ ] Modules with different SLAs (e.g., critical payments vs. reports) (+1)\\\\\\\\n- [ ] Different technologies needed per component (+1)\\\\\\\\n\\\\\\\\nResult: [X/6] — if < 3, consider a modular monolith first.\\\\\\\\n\\\\\\\\n**Alternative before microservices: Modular Monolith**\\\\\\\\n- Separate code into modules with well-defined interfaces\\\\\\\\n- Much simpler to implement and operate\\\\\\\\n- Allows extracting services gradually when needed\\\\\\\\n\\\\\\\\n## PART 2 — BOUNDED CONTEXTS IDENTIFICATION\\\\\\\\n\\\\\\\\n**Domain-Driven Design (DDD) — domain mapping:**\\\\\\\\n\\\\\\\\nBased on product type, identify bounded contexts:\\\\\\\\n\\\\\\\\n| Domain | Responsibility | Data it owns | Volume | Criticality |\\\\\\\\n|---------|----------------|--------------|--------|-------------|\\\\\\\\n| [EX: Authentication] | Login, JWT, sessions | users, sessions | Medium | Critical |\\\\\\\\n| [EX: Orders] | Order CRUD, state | orders, items | High | Critical |\\\\\\\\n| [EX: Payments] | Process, refund | payments, invoices | Medium | Critical |\\\\\\\\n| [EX: Notifications] | Email, push, SMS | notifications | High | Low |\\\\\\\\n| [EX: Analytics] | Events, reports | events, metrics | Very High | Low |\\\\\\\\n\\\\\\\\n**Golden rule**: each microservice has its own database (no service accesses another service's database directly).\\\\\\\\n\\\\\\\\n## PART 3 — PROPOSED ARCHITECTURE\\\\\\\\n\\\\\\\\n**Component diagram (describe in text):**\\\\\\\\n\\\\\\\\n\\\\\\\\\\\\\\\\\\\\\\\`\\\\\\\\\\\\\\\\\\\\\\\`\\\\\\\\\\\\\\\\\\\\\\\`\\\\\\\\n[Clients: Web / Mobile / API Partners]\\\\\\\\n          ↓\\\\\\\\n[API Gateway] — authentication, rate limiting, routing\\\\\\\\n    ↙    ↓    ↘\\\\\\\\n[Auth] [Orders] [Payments]  ← Synchronous services (REST/gRPC)\\\\\\\\n          ↓\\\\\\\\n[Message Broker: Kafka/SQS] ← Asynchronous events\\\\\\\\n    ↙         ↘\\\\\\\\n[Notifications] [Analytics]  ← Asynchronous services\\\\\\\\n\\\\\\\\\\\\\\\\\\\\\\\`\\\\\\\\\\\\\\\\\\\\\\\`\\\\\\\\\\\\\\\\\\\\\\\`\\\\\\\\n\\\\\\\\n**For each microservice, define:**\\\\\\\\n\\\\\\\\n### Service: [NAME]\\\\\\\\n- Single responsibility: [WHAT IT DOES]\\\\\\\\n- Stack: [LANGUAGE + FRAMEWORK + DATABASE]\\\\\\\\n- Interface: [REST API / gRPC / event consumer only]\\\\\\\\n- Events it publishes: [LIST]\\\\\\\\n- Events it consumes: [LIST]\\\\\\\\n- SLA: [TARGET UPTIME AND LATENCY]\\\\\\\\n- Owner team: [SQUAD]\\\\\\\\n\\\\\\\\n## PART 4 — INTER-SERVICE COMMUNICATION\\\\\\\\n\\\\\\\\n**Synchronous Communication (REST / gRPC):**\\\\\\\\n\\\\\\\\nWhen to use:\\\\\\\\n- When the client needs an immediate response\\\\\\\\n- For read operations\\\\\\\\n- For simple transactional operations\\\\\\\\n\\\\\\\\nConventions:\\\\\\\\n- REST: JSON, versioning via path (\\\\\\\\\\\\\\\\\\\\\\\`/v1/orders\\\\\\\\\\\\\\\\\\\\\\\`), correct HTTP status codes\\\\\\\\n- gRPC: for high-performance internal communication\\\\\\\\n- Circuit breaker: Resilience4j / opossum to prevent cascade failure\\\\\\\\n- Retry with exponential backoff: 3 attempts, 1s → 2s → 4s\\\\\\\\n- Timeout: define timeout per call (e.g., 5 seconds)\\\\\\\\n\\\\\\\\n**Asynchronous Communication (Kafka / SQS / RabbitMQ):**\\\\\\\\n\\\\\\\\nWhen to use:\\\\\\\\n- When the result doesn't need to be immediate\\\\\\\\n- For fanout (1 event, N consumers)\\\\\\\\n- To decouple services with different speeds\\\\\\\\n- For \\\\\\\\