Step 3 — Make the EC2 URL Static

Goal

Understand how to keep the URL stable when the EC2 public IP changes.

An EC2 instance normally receives an automatically assigned public IPv4 address.

Example:

16.16.138.182

AWS generates a public DNS name from it:

ec2-16-16-138-182.eu-north-1.compute.amazonaws.com

So:

Public IP
   ↓
AWS public DNS hostname

Important distinction

These actions normally do not require changing the public IP:

Restarting Docker
Restarting the Docker container
Updating the Docker image
Restarting Spring Boot
Rebooting the operating system

But:

EC2 Stop
   ↓
EC2 Start

can result in a different automatically assigned public IPv4 address.

Therefore the AWS-generated hostname can also change.

Option 1 — Keep the EC2 instance running

For a simple test project, this is the cheapest approach.

Use:

http://ec2-<public-ip>.<region>.compute.amazonaws.com:8080/swagger-ui/index.html

As long as the instance keeps its current public IPv4 address, the URL remains the same.

You do not need:

Domain
Route 53
Load Balancer
ECS
Fargate

This is the recommended approach if an ugly URL is completely acceptable.

Option 2 — Use an Elastic IP

If you need the public IP to remain associated with the EC2 instance across stop/start operations, AWS provides an Elastic IP.

Conceptually:

Elastic IP
    ↓
EC2
    ↓
Docker
    ↓
Spring Boot :8080

Then your endpoint can remain based on the same IP:

http://<elastic-ip>:8080/swagger-ui/index.html

Important cost warning

Do not assume an Elastic IP is free.

AWS charges for public IPv4 addresses under current pricing, including Elastic IP usage in applicable situations.

Because this project is intended to stay minimal and low-cost, use an Elastic IP only if the stable address is worth the additional cost.

What to use for this test project

If your only requirement is:

"I want a URL that lets me open my backend."

Use:

EC2 public DNS
       ↓
:8080
       ↓
Spring Boot

Example:

http://ec2-16-16-138-182.eu-north-1.compute.amazonaws.com:8080/swagger-ui/index.html

Accept that the URL can change if you stop and start the EC2 instance.

Final minimal architecture

                    Internet
                       │
                       ▼
              EC2 Public DNS
                       │
                    :8080
                       │
                       ▼
                    Docker
                       │
                       ▼
              Spring Boot Backend

No Load Balancer.

No ECS.

No Fargate.

No NAT Gateway.

No Route 53.

No domain.

No Kubernetes.

For a low-traffic test backend, this is the simplest AWS architecture.

Goal​

Important distinction​