🛢RDS Powers a Secure Three-Tier Application on AWS

Introduction:

When we design applications in the cloud, it’s not just about running code. It’s about organizing layers, controlling access, and making sure everything scales smoothly. One of the best ways to do this is through a three-tier architecture.

In this blog, I’ll walk you through how RDS fits into a three-tier app on AWS, and we’ll take a real-world Data Entry Portal as our example.

Understanding the Three Tiers

• A three-tier app is like a relay race. Each tier does its job, then hands over to the next:
• Web Tier – The entry point. This is where users connect through a browser.
• App Tier – The logic hub. It processes requests and applies business rules.
• Database Tier – The memory. It stores and retrieves data whenever the app needs it.

On AWS, these tiers are usually split like this:

• Web Tier: EC2 instances behind a Load Balancer in public subnets.
• App Tier: EC2 instances in private subnets (no direct internet access).
• DB Tier: An Amazon RDS instance running MySQL or PostgreSQL in private subnets.

Why Not Connect Directly to RDS?

Here’s a common mistake we make:

• We connect to RDS from our laptop or from a single EC2 using a public IP.

This might work in a demo, but in real projects it’s risky:

• Databases should never be publicly accessible.
• Public IPs change if EC2 is replaced.

Auto Scaling creates multiple EC2 instances, and you can’t keep whitelisting new IPs every time.

So,Use Security Groups.

Instead of allowing one IP, We allow the App Tier’s Security Group in the RDS inbound rules. That way, no matter how many EC2 instances Auto Scaling creates, they can all talk to the database securely.

Real-World Example: A Data Entry Portal

Let’s imagine an organization that runs a Data Entry Portal for its employees:

Step 1: Login through Web Tier
Employees visit the portal from their browser. The request hits the Load Balancer, which sends it to one of the web servers (EC2 in the public subnet).

Step 2: Processing in App Tier
The web server hands the request to the App Tier, where the logic runs: checking user permissions, validating data, etc.

Step 3: Secure Storage in DB Tier
Once processed, the data is stored in an Amazon RDS MySQL database. The app tier instances talk to the database via private IPs only, secured with security groups.

   Internet User
        ↓
   Load Balancer
        ↓
   Web Tier (EC2 in Public Subnet)
        ↓
   App Tier (EC2 in Private Subnet)
        ↓
   DB Tier (Amazon RDS in Private Subnet)

Why This Setup Works Well

Scalable: Auto Scaling adds EC2s without breaking DB connections.
Secure: RDS never faces the internet.
Organized: Each tier has a clear responsibility.
Real-World Ready: This is the exact setup used in enterprise portals, e-commerce sites, and SaaS platforms.

If you’re planning your first project on AWS, try this pattern—it’s simple to start with, but powerful enough to grow into large-scale applications.

Stay tuned for updates..!