Over the past few weeks, I’ve been working on a cloud infrastructure project that I’m very proud to share. This project centers around designing and deploying a highly available, secure, and scalable multi-tier architecture on Amazon Web Services (AWS). It's a great example of how we can apply core cloud and security best practices in a real-world scenario.

Let me walk you through the architecture and the thought process behind it.

Objective

To build a 3-tier web application infrastructure on AWS that emphasizes:

  • High Availability
  • Scalability
  • Security
  • Observability

This design is tailored for production-level applications with strict requirements for uptime, monitoring, and protection from external threats.

Architecture Diagram

High-Level Overview

The architecture is built within a VPC (10.0.0.0/16), split across two Availability Zones (AZ-A and AZ-B) for redundancy. It follows the standard 3-tier model:

  1. Web Tier
  2. Application Tier
  3. Integration Tier (Background Services / Async Processing)

Each tier is isolated within its own subnet and protected using security groups and routing policies.

https://dev.to/leonardkachi/building-a-scalable-secure-multi-tier-architecture-on-aws-my-recent-infrastructure-project-1a16

Key AWS Services Used

  • EC2 – For compute resources
  • ALB (Application Load Balancer) – To distribute traffic between internal services
  • ELB (External Load Balancer) – To handle incoming requests
  • Auto Scaling – To ensure each tier can scale based on demand
  • S3 – For static content and logs
  • RDS – For managed relational database service
  • EFS – For shared storage across AZs
  • IAM – To manage fine-grained access controls
  • CloudWatch – For monitoring and logging
  • Route 53 – For DNS resolution
  • VPC Flow Logs – For traffic visibility and security analysis
  • CloudFront – For CDN distribution (static assets and caching)

Detailed Architecture Breakdown

1. Web Tier (Frontend)

  • Deployed across two public subnets.
  • EC2 instances serve the frontend (Apache/NGINX or Node.js apps).
  • Protected by an External ALB that routes traffic using HTTPS (SSL termination).
  • Auto Scaling Groups handle traffic spikes and maintain instance health.
  • Integrated with CloudFront to serve cached content quickly.

2. Application Tier

  • Deployed in private subnets for better security.
  • Hosts core business logic on EC2, registered under an Internal ALB.
  • Communicates with both the web and integration tiers.
  • IAM roles restrict access to specific AWS services (e.g., S3, RDS).

3. Integration Tier

  • Handles background tasks and async processes (e.g., job queues, processing pipelines).
  • Also deployed in private subnets.
  • This layer is decoupled and communicates directly with the Application Tier and services like RDS or S3.
  • All logs and outputs are pushed to S3 and CloudWatch.

Security Best Practices

  • Layered Security: Subnets and security groups segment each layer.
  • Least Privilege: IAM roles and policies are tightly scoped.
  • No Public Access to App/Integration Tiers: Only the Web Tier is exposed via the External Load Balancer.
  • VPC Flow Logs track traffic patterns and are fed into SIEM tools for analysis.
  • Data Encryption: At rest (S3, RDS, EFS) and in transit (HTTPS).

Resilience & Observability

  • Health checks and auto-scaling across AZs provide fault tolerance.
  • CloudWatch metrics, alarms, and dashboards offer real-time observability.
  • Application logs and metrics are centralized in CloudWatch and S3 for auditing and debugging.

What’s Next?

  • Integrating AWS WAF and Shield for advanced threat protection.
  • Enabling DynamoDB and Lambda-based background workers in the integration tier.
  • Automating the entire infrastructure using Terraform and CI/CD pipelines for streamlined deployment.

Final Thoughts

This project pushed me deeper into cloud security, automation, and architecture design. It solidified my understanding of multi-tier deployments and sharpened my focus on resilience and compliance in production systems.

If you're building a cloud-native app or looking to secure a modern SaaS workload on AWS, this kind of architecture offers a robust foundation.

Feel free to connect if you'd like to collaborate or brainstorm ideas — I'm always open to meaningful conversations around Cloud Security, DevSecOps, and AI-driven Infrastructure.