Skip to main content

Our Architecture!

AWS VPC Architecture Documentation: Multi-Tier Application with Public-Private Subnet Design

1. Architecture Overview​

This AWS VPC architecture implements a secure, scalable, and highly available infrastructure design using a multi-tier approach with public and private subnets across multiple Availability Zones (AZs). The architecture is specifically designed to host applications that require internet accessibility while maintaining secure internal components.

2. Core Components​

2.1 Entry Points​

API Gateway​

  • Serves as the primary entry point for API requests
  • Provides API versioning, throttling, and security features
  • Enables RESTful API interfaces for the application
  • Handles authentication and authorization at the API level

Public Load Balancer​

  • Distributes incoming traffic across multiple instances
  • Performs health checks on target instances
  • Provides SSL/TLS termination
  • Enables high availability and fault tolerance

2.2 Networking Components​

Public Subnets​

Purpose: Host internet-facing resources that need to directly communicate with external clients

Components:

  • EC2 instances (Web/Application servers)
  • NAT Gateways (for enabling private subnet internet access)
  • Load Balancers

Characteristics:

  • Direct route to Internet Gateway
  • Public IP addresses available
  • Accessible from the internet
  • Located in multiple AZs for redundancy

Private Subnets​

Purpose: Host internal resources that should not be directly accessible from the internet

Components:

  • Amazon RDS instances
  • Redis Cache
  • Internal application servers
  • Database Migration Service (DMS)

Characteristics:

  • No direct internet access
  • Access internet through NAT Gateway
  • Enhanced security for sensitive resources
  • Spread across multiple AZs

3. Communication Flow​

3.1 Inbound Traffic Flow​

  1. External requests arrive at API Gateway
  2. Requests are forwarded to the Public Load Balancer
  3. Load Balancer distributes traffic to EC2 instances in public subnets
  4. Public subnet EC2 instances process requests and communicate with private subnet resources as needed

3.2 Internal Communication​

  • Public subnet resources communicate with private subnet resources through internal VPC networking
  • Private subnet resources can communicate with each other within the VPC
  • Database connections are established only from application servers to RDS instances
  • Redis cache is accessed by application servers for improved performance

3.3 Outbound Traffic Flow​

  • Private subnet resources access internet through NAT Gateway in public subnet
  • Public subnet resources can directly access internet through Internet Gateway
  • All outbound traffic is logged and monitored

4. Security Implementation​

4.1 Network Access Control​

Network ACLs (NACLs):​

  • Stateless firewall at subnet level
  • Controls inbound and outbound traffic
  • Provides additional security layer

Security Groups:​

  • Instance-level firewall
  • Stateful traffic control
  • Fine-grained access control

4.2 Access Patterns​

  • Public subnet resources: Limited to necessary inbound ports (e.g., 80, 443)
  • Private subnet resources: No direct inbound access from internet
  • Database access: Restricted to application servers only
  • Cache access: Limited to application tier

5. Benefits of this Architecture​

5.1 Security Benefits​

  • Isolated database and cache layers
  • Defense in depth through multiple security layers
  • Controlled internet access
  • Protected sensitive resources
  • Reduced attack surface

5.2 Availability Benefits​

  • Multi-AZ deployment
  • Automatic failover capabilities
  • Load balancing across instances
  • High availability for all tiers
  • Disaster recovery readiness

5.3 Scalability Benefits​

  • Horizontal scaling capability
  • Independent scaling of components
  • Auto-scaling support
  • Load balancer integration
  • Flexible resource allocation

5.4 Performance Benefits​

  • Distributed cache layer
  • Optimized network paths
  • Load distribution
  • Reduced latency through proper placement
  • Enhanced database performance

6. Use Cases for this Architecture​

6.1 Ideal Scenarios​

  • Web applications with database backend
  • Microservices architectures
  • E-commerce platforms
  • Enterprise applications
  • API-based services

6.2 Workload Types​

  • Multi-tier applications
  • Stateless applications
  • Database-driven applications
  • Cache-dependent services
  • API-driven systems

7. Best Practices Implementation​

7.1 Infrastructure Design​

  • Redundancy across AZs
  • Proper subnet sizing
  • Efficient CIDR block allocation
  • Scalable component placement
  • Future growth consideration

7.2 Security Measures​

  • Principle of least privilege
  • Network segregation
  • Access control implementation
  • Security group design
  • Encryption implementation

7.3 Monitoring and Maintenance​

  • CloudWatch integration
  • Logs aggregation
  • Performance monitoring
  • Resource utilization tracking
  • Automated alerting

8. Cost Optimization​

8.1 Resource Optimization​

  • Right-sizing instances
  • Auto-scaling implementation
  • Reserved instance usage
  • Storage optimization
  • Network transfer optimization

8.2 Operational Efficiency​

  • Automated management
  • Simplified maintenance
  • Reduced operational overhead
  • Efficient resource utilization
  • Optimized performance

9. Conclusion​

This architecture provides a robust, secure, and scalable foundation for modern applications. It balances security requirements with performance needs while ensuring high availability and maintainability. The clear separation of public and private resources, combined with proper security controls and redundancy, makes it suitable for enterprise-grade applications.

10. Recommendations​

10.1 Implementation Recommendations​

  • Regular security audits
  • Performance monitoring setup
  • Disaster recovery planning
  • Backup strategy implementation
  • Documentation maintenance

10.2 Future Considerations​

  • Container adoption strategy
  • Serverless integration
  • Multi-region expansion
  • Enhanced monitoring
  • Security enhancement plans