# Research: Lab 05 - Database & RDS

**Objective:** Simulate AWS RDS (Relational Database Service) using PostgreSQL in Docker private network.

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## Domain Research

### PostgreSQL in Docker

**Official Image:** `postgres:16-alpine`
- Lightweight Alpine-based PostgreSQL
- Default port: 5432
- Environment variables for configuration:
  - `POSTGRES_DB`: Database name
  - `POSTGRES_USER`: Username
  - `POSTGRES_PASSWORD`: Password
  - `POSTGRES_INITDB_ARGS`: Initialization arguments

**Healthcheck:** `pg_isready` command
- Tests if PostgreSQL is ready to accept connections
- Returns 0 if ready, non-zero if not ready

### RDS Concepts

**AWS RDS Features:**
- Managed database service
- Deployed in VPC private subnets
- Automated backups (not simulating in lab)
- Multi-AZ deployment (not simulating in lab)
- Resource limits (instance classes)
- Encryption at rest (not simulating in lab)

**Instance Classes (for PARALLELISM):**
- db.t2.micro: 1 vCPU, 1 GB RAM
- db.t2.small: 1 vCPU, 2 GB RAM
- db.t2.medium: 2 vCPU, 4 GB RAM

### Integration with Previous Labs

**Lab 01 (IAM):** Non-root containers
- PostgreSQL container must NOT run as root

**Lab 02 (Network):** Private networks
- Database must be in private network
- NO ports exposed on host

**Lab 03 (Compute):** Resource limits
- PostgreSQL must have CPU/memory limits

**Lab 04 (Storage):** Named volumes
- Database data must persist in named volume

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## Common Pitfalls

1. **Database accessible from host**
   - Must NOT expose ports on host
   - Only accessible from containers in same private network

2. **Data loss on container restart**
   - Must use named volume for data directory
   - Volume must persist across container lifecycle

3. **Running as root**
   - PostgreSQL image runs as postgres user by default
   - Must verify non-root execution

4. **No resource limits**
   - Must configure cpus and memory limits
   - Prevents database from consuming all host resources

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## Testing Strategy

### RED Phase Tests (Plan 06-01)

1. **Database Creation Test**
   - Verify container starts successfully
   - Verify database is initialized
   - Verify pg_isready works

2. **Private Network Test**
   - Verify database is in private network
   - Verify NOT accessible from host
   - Verify accessible from same network

3. **Persistence Test**
   - Create test data
   - Stop container
   - Start container
   - Verify data still exists

4. **Security Test**
   - INF-01: Non-root user
   - INF-02: No host port bindings
   - INF-03: Resource limits
   - INF-04: Named volume

### GREEN Phase Implementation (Plan 06-03)

- docker-compose.yml with PostgreSQL in private network
- Named volume for data persistence
- Resource limits for CPU/memory
- Healthcheck configuration
- No host port bindings (INF-02)

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## Cloud Parallels (PARA-01/02/03/04)

| Local Concept | AWS Equivalent | Parallel |
|---------------|----------------|----------|
| PostgreSQL container | RDS Instance | Managed database |
| Private network | VPC Private Subnet | Isolated deployment |
| Named volume | EBS volume | Data persistence |
| Resource limits | Instance class | Compute allocation |
| No root access | AWS IAM authentication | Access control |
| pg_isready | RDS health check | Availability check |