# Deployment Guide

This guide provides comprehensive instructions for deploying the DBIS Core Banking System to production.

## Deployment Architecture

```mermaid
graph TB
    subgraph "Production Environment"
        LB[Load Balancer]
        
        subgraph "Application Tier"
            APP1[App Instance 1]
            APP2[App Instance 2]
            APPN[App Instance N]
        end
        
        subgraph "Database Tier"
            DB_PRIMARY[(Primary Database)]
            DB_REPLICA1[(Replica 1)]
            DB_REPLICA2[(Replica 2)]
        end
        
        subgraph "Cache Tier"
            CACHE1[(Redis 1)]
            CACHE2[(Redis 2)]
        end
        
        subgraph "Monitoring"
            METRICS[Metrics Collector]
            LOGS[Log Aggregator]
        end
        
        LB --> APP1
        LB --> APP2
        LB --> APPN
        
        APP1 --> DB_PRIMARY
        APP2 --> DB_PRIMARY
        APPN --> DB_PRIMARY
        
        DB_PRIMARY --> DB_REPLICA1
        DB_PRIMARY --> DB_REPLICA2
        
        APP1 --> CACHE1
        APP2 --> CACHE2
        
        APP1 --> METRICS
        APP2 --> METRICS
        APPN --> METRICS
        
        APP1 --> LOGS
        APP2 --> LOGS
        APPN --> LOGS
    end
```

## CI/CD Pipeline

```mermaid
graph LR
    subgraph "CI/CD Pipeline"
        COMMIT[Git Commit]
        BUILD[Build]
        TEST[Run Tests]
        LINT[Lint & Format]
        SECURITY[Security Scan]
        DEPLOY[Deploy]
    end
    
    COMMIT --> BUILD
    BUILD --> TEST
    TEST --> LINT
    LINT --> SECURITY
    SECURITY --> DEPLOY
```

## Production Setup

### Environment Variables

All required environment variables must be set in production:

- `DATABASE_URL` - PostgreSQL connection string
- `JWT_SECRET` - Must be at least 32 characters, use strong random string
- `ALLOWED_ORIGINS` - Comma-separated list of allowed CORS origins (no wildcards)
- `NODE_ENV` - Set to `production`
- `LOG_LEVEL` - Recommended: `info` or `warn`
- `HSM_ENABLED` - Set to `true` if using HSM hardware

### Database Migrations

1. Generate Prisma client:
   ```bash
   npx prisma generate
   ```

2. Run migrations:
   ```bash
   npx prisma migrate deploy
   ```

3. Verify migration status:
   ```bash
   npx prisma migrate status
   ```

### Build Process

1. Install dependencies:
   ```bash
   npm ci
   ```

2. Generate Prisma client:
   ```bash
   npx prisma generate
   ```

3. Build TypeScript:
   ```bash
   npm run build
   ```

4. Start the application:
   ```bash
   npm start
   ```

### Health Checks

The application provides a health check endpoint at `/health` that verifies:
- Database connectivity
- HSM availability (if enabled)
- Application status

### Monitoring Setup

1. Configure logging to external service (if needed)
2. Set up metrics collection (Prometheus)
3. Configure alerting for critical errors
4. Monitor database performance

### Security Checklist

- [ ] All environment variables validated
- [ ] JWT_SECRET is strong and secure
- [ ] CORS origins are properly configured
- [ ] HSM is enabled and configured
- [ ] Database credentials are secure
- [ ] Rate limiting is configured
- [ ] Security headers are enabled (Helmet)
- [ ] Audit logging is enabled

### Scaling Considerations

- Use connection pooling for database
- Consider horizontal scaling with load balancer
- Monitor resource usage
- Set up database read replicas if needed

## Deployment Recommendations

### Infrastructure as Code

**Priority: High**

1. **Infrastructure Automation**
   - **Description**: Use Infrastructure as Code (IaC) for all infrastructure
   - **Implementation**: 
     - Use Terraform or CloudFormation
     - Version control infrastructure code
     - Automate provisioning and updates
   - **Impact**: Ensures consistent infrastructure and reduces manual errors
   - **Dependencies**: IaC tool configured, cloud provider access

2. **Environment Management**
   - **Description**: Separate environments for dev, staging, production
   - **Implementation**: 
     - Use environment-specific configurations
     - Never use production data in dev
     - Secure environment variables
   - **Impact**: Prevents production issues and data leaks
   - **Dependencies**: Environment separation configured

### Deployment Strategy

**Priority: High**

1. **Blue-Green Deployment**
   - **Description**: Implement blue-green deployment strategy
   - **Implementation**: 
     - Deploy new version alongside current version
     - Switch traffic after validation
     - Keep previous version for rollback
   - **Impact**: Enables zero-downtime deployments
   - **Dependencies**: Load balancer, deployment automation

2. **Database Migration Strategy**
   - **Description**: Safe database migration process
   - **Implementation**: 
     - Test migrations in staging
     - Backup before migrations
     - Plan rollback procedures
     - Use migration versioning
   - **Impact**: Prevents data loss and downtime
   - **Dependencies**: Database backup system, migration tools

### Monitoring & Alerting

**Priority: Critical**

1. **Health Monitoring**
   - **Description**: Comprehensive health monitoring
   - **Implementation**: 
     - Monitor application health endpoints
     - Track database connectivity
     - Monitor HSM availability
     - Set up alerting for failures
   - **Impact**: Enables proactive issue detection
   - **Dependencies**: Monitoring infrastructure, alerting system

2. **Performance Monitoring**
   - **Description**: Monitor system performance
   - **Implementation**: 
     - Track API response times
     - Monitor database query performance
     - Track resource utilization
     - Set performance alerts
   - **Impact**: Enables performance optimization
   - **Dependencies**: APM tools, metrics collection

### Disaster Recovery

**Priority: Critical**

1. **Backup Strategy**
   - **Description**: Automated backup system
   - **Implementation**: 
     - Daily full backups
     - Hourly incremental backups
     - Store backups in multiple locations
     - Test restore procedures regularly
   - **Impact**: Enables recovery from data loss
   - **Dependencies**: Backup storage, backup automation

2. **Multi-Region Deployment**
   - **Description**: Deploy across multiple regions
   - **Implementation**: 
     - Deploy active-active in primary regions
     - Implement cross-region replication
     - Test failover procedures
     - Monitor cross-region latency
   - **Impact**: Ensures availability during regional outages
   - **Dependencies**: Multi-region infrastructure, replication configured

For more detailed recommendations, see [RECOMMENDATIONS.md](./RECOMMENDATIONS.md) and [monitoring.md](./monitoring.md).

