Two-Tier Architecture with VPC and Load Balancer
This is a real-world, practical cloud project — something you'd actually use in a industry professional environment.
We’ve built a two-tier architecture on AWS that is scalable, secure, and cost-effective. The goal? To run a web application that can handle users, store data safely, and keep running even if something fails.
To understand how this architecture works and why it’s important, we first need to understand the foundational building block of cloud infrastructure — Amazon VPC.
Let's Understand VPC in Simple Terms
Let's understand one of the most complicated topics in cloud computing — a topic many people generally find difficult. In this section, we’ll break down what a VPC is, why we need it, and what its components are.
What is a VPC?
You can consider it as your virtual data center and virtual private network in the cloud.
A VPC (Virtual Private Cloud) is your isolated space within AWS where you can launch AWS resources in a network that you define and control.
What if VPC didn't exist?
Let's understand this with a simple scenario. If company A is not following standard security practices and doesn't use a properly isolated network like VPC, then other companies sharing the same data center could potentially face data breaches and hacking attempts — all because of company A.
VPCs help prevent such risks by isolating each organization's resources from others within the same cloud provider.
Why Do We Need a VPC?
Let’s take a real-life example:
A college student wants to start a company. Managing physical servers and the underlying infrastructure is costly and hectic for him, so he uses a VPC to set up his servers and database virtually — saving cost, time, and effort.
Using a VPC allows him to focus on building his product while AWS handles the heavy lifting of infrastructure, security, and scalability.
How Does Data Flow Through a VPC?
To better understand the internal routing, here’s how data flows through various VPC components:
This diagram helps visualize how requests travel from the internet, through the load balancer and public subnets, down to private subnets where your app and database live securely.
Components of a VPC
When you create a VPC, you’re essentially building your own virtual network with the following components:
- Subnets: Logical subdivisions of your network (public and private)
- Route Tables: Control how traffic flows within your VPC
- Internet Gateway (IGW): Enables internet access for public subnets
- NAT Gateway: Allows private instances to securely access the internet
- Security Groups & NACLs: Act like firewalls to control inbound/outbound traffic
- Elastic IPs & Endpoints: Help in external accessibility and private service connections
With this solid networking foundation in place, we now move to a critical part of building a reliable system — distributing traffic efficiently using Load Balancers.
What is a Load Balancer?
A Load Balancer acts as a traffic distributor. It routes incoming requests to multiple backend servers to ensure high availability, reliability, and fault tolerance.
AWS provides Elastic Load Balancing (ELB) to manage this distribution seamlessly across multiple targets such as EC2 instances, containers, and IP addresses.
Load Balancers are essential when building scalable systems that need to stay online even when one or more components fail.
Types of Load Balancers in AWS
Depending on your application’s needs, AWS offers three types of load balancers:
| Load Balancer | OSI Layer | Best For | Real-World Use Case |
|---|---|---|---|
| Application Load Balancer (ALB) | Layer 7 | HTTP/HTTPS traffic | Routing user requests to different microservices based on URL paths (e.g., /login → auth server, /api → backend) |
| Network Load Balancer (NLB) | Layer 4 | High-performance, TCP/UDP traffic | Real-time multiplayer gaming app or stock trading platform where low latency is critical |
| Gateway Load Balancer (GWLB) | Layer 3 | Deploying virtual appliances | Centralizing third-party firewall inspection in a hub-and-spoke architecture |
Each type plays a different role depending on how you want to manage traffic, security, and application logic.
That’s it for the architecture and concept explanation. In the next part, I’ll show you how to implement this entire two-tier architecture on AWS with step-by-step instructions.
✍️ Author: Omkar Sharma
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