# AWS Best Practices

## Security Best Practices

### Identity and Access Management (IAM)
- **Principle of Least Privilege**: Grant only the minimum permissions needed
- **Use IAM Roles**: Prefer roles over long-term access keys
- **Enable MFA**: Multi-factor authentication for all users
- **Regular Access Reviews**: Audit and remove unused permissions

### Data Protection
- **Encryption at Rest**: Use AWS KMS for data encryption
- **Encryption in Transit**: Use TLS/SSL for all communications
- **Backup Strategy**: Regular backups with cross-region replication
- **Data Classification**: Classify and protect sensitive data appropriately

### Network Security
- **VPC Design**: Use private subnets for sensitive resources
- **Security Groups**: Implement least-privilege network access
- **NACLs**: Additional layer of network security
- **VPN/Direct Connect**: Secure connectivity to on-premises

## Cost Optimization

### Resource Management
- **Right-Sizing**: Match instance types to workload requirements
- **Reserved Instances**: Use RIs for predictable workloads
- **Spot Instances**: Leverage spot instances for fault-tolerant workloads
- **Auto Scaling**: Automatically adjust capacity based on demand

### Monitoring & Analysis
- **Cost Explorer**: Regular cost analysis and trending
- **Budgets & Alerts**: Set up cost monitoring and alerts
- **Resource Tagging**: Consistent tagging for cost allocation
- **Trusted Advisor**: Use recommendations for cost optimization

### Storage Optimization
- **S3 Storage Classes**: Use appropriate storage classes for data lifecycle
- **EBS Optimization**: Right-size volumes and use appropriate types
- **Data Lifecycle**: Implement policies for data archival and deletion
- **CloudFront**: Use CDN to reduce data transfer costs

## Reliability & Performance

### High Availability
- **Multi-AZ Deployment**: Deploy across multiple availability zones
- **Auto Scaling**: Automatic capacity adjustment
- **Load Balancing**: Distribute traffic across multiple instances
- **Health Checks**: Monitor and replace unhealthy instances

### Disaster Recovery
- **Backup Strategy**: Regular, tested backups
- **Cross-Region Replication**: Replicate critical data across regions
- **Recovery Testing**: Regular disaster recovery drills
- **RTO/RPO Planning**: Define recovery time and point objectives

### Performance Optimization
- **CloudWatch Monitoring**: Monitor key performance metrics
- **Performance Testing**: Regular load and stress testing
- **Caching Strategies**: Use ElastiCache and CloudFront
- **Database Optimization**: Optimize queries and use read replicas

## Operational Excellence

### Monitoring & Logging
- **CloudWatch**: Comprehensive monitoring and alerting
- **CloudTrail**: API call logging and auditing
- **VPC Flow Logs**: Network traffic monitoring
- **Application Logs**: Centralized logging with CloudWatch Logs

### Automation
- **Infrastructure as Code**: Use CloudFormation or Terraform
- **CI/CD Pipelines**: Automated deployment pipelines
- **Configuration Management**: Use Systems Manager or similar tools
- **Automated Remediation**: Self-healing systems where possible

### Documentation & Procedures
- **Architecture Documentation**: Keep architecture diagrams current
- **Runbooks**: Document operational procedures
- **Incident Response**: Clear incident response procedures
- **Change Management**: Controlled change processes

## Well-Architected Framework

### Five Pillars
1. **Operational Excellence**: Run and monitor systems effectively
2. **Security**: Protect information and systems
3. **Reliability**: Recover from failures and meet demand
4. **Performance Efficiency**: Use resources efficiently
5. **Cost Optimization**: Avoid unnecessary costs

### Design Principles
- **Design for Failure**: Assume components will fail
- **Decouple Components**: Reduce dependencies between components
- **Implement Elasticity**: Scale resources based on demand
- **Think Parallel**: Parallelize operations where possible
- **Leverage Managed Services**: Use AWS managed services when appropriate

## Service-Specific Best Practices

### EC2
- Use appropriate instance types for workloads
- Implement proper security groups and key management
- Regular patching and updates
- Monitor performance and right-size instances

### S3
- Use bucket policies and IAM for access control
- Enable versioning for important data
- Implement lifecycle policies for cost optimization
- Use CloudFront for global content distribution

### RDS
- Use Multi-AZ for high availability
- Implement automated backups and point-in-time recovery
- Monitor performance with Performance Insights
- Use read replicas for read-heavy workloads

### Lambda
- Optimize function memory and timeout settings
- Use environment variables for configuration
- Implement proper error handling and retries
- Monitor with CloudWatch and X-Ray
