Application Load Balancer (ALB) in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an Application Load Balancer (ALB) in AWS?

An Application Load Balancer (ALB) is a service that distributes incoming application traffic across multiple targets, such as EC2 instances, containers, and IP addresses, to improve availability and scalability.

intermediate

How does ALB differ from a Classic Load Balancer (CLB)?

ALB works at the application layer (Layer 7) and supports advanced routing like path-based and host-based routing, while CLB works at both Layer 4 and Layer 7 but with fewer features and less flexibility.

intermediate

What types of routing can ALB perform?

ALB supports path-based routing (routing based on URL paths), host-based routing (routing based on domain names), and supports routing based on HTTP headers, methods, and query parameters.

beginner

What is a target group in the context of ALB?

A target group is a set of resources (like EC2 instances or IP addresses) that ALB routes traffic to. You can register or deregister targets dynamically to manage traffic flow.

beginner

Why is health checking important in ALB?

Health checks monitor the status of targets to ensure ALB only sends traffic to healthy instances, improving reliability and user experience.

Which layer of the OSI model does an Application Load Balancer operate on?

A Layer 7 (Application Layer)

B Layer 4 (Transport Layer)

C Layer 3 (Network Layer)

D Layer 2 (Data Link Layer)

ALB operates at Layer 7, allowing it to make routing decisions based on application-level data like HTTP headers and paths.

What feature allows ALB to route traffic based on URL paths?

A Path-based routing

B Host-based routing

C IP-based routing

D Port-based routing

Path-based routing lets ALB send requests to different targets depending on the URL path.

Which of the following is NOT a valid target type for ALB?

A EC2 instances

B Lambda functions

C IP addresses

D Containers

ALB does not directly support Lambda functions as targets; that is supported by AWS Lambda with API Gateway or Network Load Balancer with Lambda integration.

What happens if a target fails health checks in ALB?

A ALB reroutes traffic to the client

B Traffic is still sent to the target

C ALB shuts down

D Traffic is stopped to that target until it passes health checks

ALB stops sending traffic to unhealthy targets to maintain service reliability.

Which AWS service is commonly used with ALB to automatically scale targets?

A AWS CloudTrail

B AWS S3

C AWS Auto Scaling

D AWS IAM

AWS Auto Scaling adjusts the number of targets based on demand, working with ALB to handle traffic efficiently.

Explain how an Application Load Balancer improves application availability and scalability.

Think about how traffic is shared and how failures are handled.

Describe the difference between path-based and host-based routing in ALB.

Consider what part of the request ALB looks at to route.