nicholastcs/three-tier-architecture

Three-tier architecture

Diagram below shows a simple three-tier architecture that consists of Web-tier, App-tier and DB-tier. This system span across 3 availability zones.

Summary

• The public subnet is used to store bastion host instances, which serve as a jump host to the instances at app-tier subnet and web-tier subnet.

• The web-tier subnet is used to accomodate EC2 instances that serves static front-end web contents. The EC2 inside will communicate with app-tier subnet's EC2 through internal ALB. Autoscaling group will help to provision more instances when there is a spike on CPU utilization.

• The app-tier subnet is used to accomodate EC2 instances that serves business logic apps. The EC2 will receive request from instances in web-tier subnet's EC2 through internal ALB.

• The DB-tier subnet is used to accomodate database instances.

Build sequence

1. networking/
2. lb/
3. db/
4. web/
5. app/*

Pre-requisites

• Ubuntu or WSL2

• Terraform v1.0.6 (https://releases.hashicorp.com/terraform/1.0.6/)

• Terraform-docs (https://github.com/terraform-docs/terraform-docs)

• Pre-commit (https://pre-commit.com/#install), be sure to run pre-commit install.