Share the crowd across servers — Elastic Load Balancing and EC2

Your goal

Give a busy website one entry point that can use several app servers.

Why this matters

One server can become overloaded or fail. You will place a load balancer, define a health check, and route visitors to the right app.

Words you will use

A load balancer distributes requests. A target is a server or app that receives them. A listener accepts traffic on a chosen port.

How to proceed

Read each situation and choose an answer. The lesson explains the result. Try again if needed, then continue through all three decisions and finish the tour.

1. Put a greeter at the door

Your site has two app servers. Visitors need one address, and incoming work should be shared across those servers. Choose the entry point.

What belongs in front of the app servers?

An Application Load Balancer.

The load balancer receives web traffic and sends requests to targets in a target group. A single public entry point can lead to more than one app server.

The website has one front door and several possible workers.

Browser → load balancer → target group

2. Check whether an app is ready

A server is on, but its web app has crashed. With another healthy target available, you want traffic to avoid the broken app. Choose what a health check should test.

What is the useful check?

A suitable app endpoint that reports readiness.

A health check asks whether the target can serve requests. Pick a path that reflects your app’s readiness and monitor failures. An all-unhealthy group needs its own recovery plan.

The balancer can distinguish a healthy app from an unusable one.

Health check: HTTP /health → expected success response

3. Send requests to the right app

The same site serves photos under /photos and orders under /orders. Each has its own target group. Choose how the entry point should pick one.

What maps a path to a target group?

Listener rules that match request paths.

An Application Load Balancer can use request information such as path to choose a target group. Review rule priority and the default rule too.

Photo requests and order requests go to their intended apps.

/photos/* → photos group
/orders/* → orders group

Practice, then check your understanding

In the interactive tour, make each decision before seeing the outcome. Wrong answers receive coaching, and replay gives you a fresh attempt without duplicating earned XP.

Read the official AWS documentation for service behavior and production details.