# Architecture Examples
> Real-world architecture decisions by project type.
---
## Example 1: MVP E-commerce (Solo Developer)
```yaml
Requirements:
- <1000 users initially
- Solo developer
- Fast to market (8 weeks)
- Budget-conscious
Architecture Decisions:
App Structure: Monolith (simpler for solo)
Framework: Next.js (full-stack, fast)
Data Layer: Prisma direct (no over-abstraction)
Authentication: JWT (simpler than OAuth)
Payment: Stripe (hosted solution)
Database: PostgreSQL (ACID for orders)
Trade-offs Accepted:
- Monolith → Can't scale independently (team doesn't justify it)
- No Repository → Less testable (simple CRUD doesn't need it)
- JWT → No social login initially (can add later)
Future Migration Path:
- Users > 10K → Extract payment service
- Team > 3 → Add Repository pattern
- Social login requested → Add OAuth
```
---
## Example 2: SaaS Product (5-10 Developers)
```yaml
Requirements:
- 1K-100K users
- 5-10 developers
- Long-term (12+ months)
- Multiple domains (billing, users, core)
Architecture Decisions:
App Structure: Modular Monolith (team size optimal)
Framework: NestJS (modular by design)
Data Layer: Repository pattern (testing, flexibility)
Domain Model: Partial DDD (rich entities)
Authentication: OAuth + JWT
Caching: Redis
Database: PostgreSQL
Trade-offs Accepted:
- Modular Monolith → Some module coupling (microservices not justified)
- Partial DDD → No full aggregates (no domain experts)
- RabbitMQ later → Initial synchronous (add when proven needed)
Migration Path:
- Team > 10 → Consider microservices
- Domains conflict → Extract bounded contexts
- Read performance issues → Add CQRS
```
---
## Example 3: Enterprise (100K+ Users)
```yaml
Requirements:
- 100K+ users
- 10+ developers
- Multiple business domains
- Different scaling needs
- 24/7 availability
Architecture Decisions:
App Structure: Microservices (independent scale)
API Gateway: Kong/AWS API GW
Domain Model: Full DDD
Consistency: Event-driven (eventual OK)
Message Bus: Kafka
Authentication: OAuth + SAML (enterprise SSO)
Database: Polyglot (right tool per job)
CQRS: Selected services
Operational Requirements:
- Service mesh (Istio/Linkerd)
- Distributed tracing (Jaeger/Tempo)
- Centralized logging (ELK/Loki)
- Circuit breakers (Resilience4j)
- Kubernetes/Helm
```
