# Technology Selection

## Database Selection

Decision factors:

1. **Data model fit**
   - Relational (structured, ACID, complex queries) → PostgreSQL, MySQL
   - Document (flexible schema, nested data) → MongoDB, DynamoDB
   - Graph (relationship-heavy) → Neo4j, DGraph
   - Time-series (metrics, events) → TimescaleDB, InfluxDB
   - Key-value (simple lookups, cache) → Redis, DynamoDB

2. **Consistency requirements**
   - Strong consistency → PostgreSQL, CockroachDB
   - Eventual consistency acceptable → DynamoDB, Cassandra
   - Hybrid needs → MongoDB, Cosmos DB

3. **Scale characteristics**
   - Read-heavy → read replicas, caching
   - Write-heavy → sharding, write-optimized DB
   - Both → consider CQRS pattern

4. **Operational complexity**
   - Managed service available? Use it unless special needs
   - Self-hosted required? Factor operational overhead
   - Multi-region? Consider distributed databases

Decision matrix:

```
ACID + complex queries + proven? → PostgreSQL
Flexibility + horizontal scaling + managed? → DynamoDB
Document model + rich queries + open source? → MongoDB
High write throughput + wide column? → Cassandra
Caching + pub/sub + simple data? → Redis
```

## Framework Selection

### Backend (TypeScript/JavaScript)

| Framework | Best for |
|-----------|----------|
| Hono | New projects, serverless, edge |
| Express | Teams with Express experience |
| Fastify | Raw speed matters |
| NestJS | Large teams, complex domains |

### Backend (Rust)

| Framework | Best for |
|-----------|----------|
| Axum | New projects, type-safe routing |
| Actix-web | Raw performance critical |
| Rocket | Rapid development |

Decision criteria:
- Team expertise and learning curve
- Performance requirements (most apps don't need Rust speed)
- Ecosystem and library availability
- Type safety and developer experience
- Deployment target (serverless, containers, bare metal)

### Frontend

| Stack | Best for |
|-------|----------|
| React + TanStack Router | Complex state, large ecosystem |
| Solid | Performance-critical UIs |
| Svelte | Small teams, simple apps |
| Next.js | SSR/SSG needs, full-stack React |

## Infrastructure

### Serverless (Vercel, Cloudflare Workers, AWS Lambda)

- **Pros**: Zero ops, auto-scaling, pay-per-use
- **Cons**: Cold starts, vendor lock-in, harder debugging
- **Best for**: Low-traffic apps, edge functions, prototypes

### Container orchestration (Kubernetes, ECS)

- **Pros**: Portability, fine control, proven at scale
- **Cons**: Operational complexity, learning curve
- **Best for**: Medium-large apps, multi-service systems

### Platform-as-a-Service (Heroku, Render, Railway)

- **Pros**: Simple deploys, managed infrastructure
- **Cons**: Higher cost, less control, scaling limits
- **Best for**: Startups, MVPs, small teams

### Bare metal / VMs

- **Pros**: Full control, cost-effective at scale
- **Cons**: High operational burden
- **Best for**: Special requirements, very large scale