HA Elastic Load Balancers

Question 1

What are the three types of Elastic Load Balancers and their use case?

Answer 1

1. Application Load Balancer - are best suted for load balancing of HTTP and HTTPS traiffc. They operate at layer 7 and are application awarey. They are intelligent, and you can create advanced request routing, sending specific request to specific web servers.
2. Network Load Balancer - are best suited for load balancing of TCP traffic where extreme performance is required. Operating at the connection layer, (Layer 4), NLBs are capable of handling million of requests per second, while maintaining ultra-low latencies. Use for extreme performance.
3. Classic Load Balancer -
   are the legacy Elastic Load Balancers. You can load balance HTTP/HTTPS applications and use Layer 7 specific features, such as X-Forwarded and sticky sessions. You can also use strict Layer 4 load balancing for applications that rely purely on the TCP protocol.

Question 2

What are the Elastic Load Balancer Exam Tips?

Answer 2

1. Name and describe the three types of Load Balancers.
2. Know that a 504 error means the gateway has timed out. This means that the application is not responding in the idle timeout period.
3. Troubleshooting the application. Is it the web or database server?
4. If you need the IPv4 address of your end user, look for the X-Forwarded-For header.
5. Instances monitored by ELB as in or out of service.
6. Health Checks check the instance by talking to it.
7. Read the ELB FAQ for Classic Load Balancers.

Question 3

(Advanced Load Balancers) What are Sticky Sessions?

Answer 3

Classic Load Balancer routes each request independently to the registered EC2 instance with the smallest load.

Sticky Sessions allow you to bind a users sessions to a specific EC2 instance. This ensures that all request from the user during the session are sent to the same instance.

You can enable sticky sessions for ALBs as well, but the traffic will be sent at the Target Group Level.

Question 4

(Advanced Load Balancers) What is Cross Load Balancing?

Answer 4

With cross-zone load balancing, each load balancer node for your Classic Load Balancer distributes requests evenly across the registered instances in all enabled Availability Zones. If cross-zone load balancing is disabled, each load balancer node distributes requests evenly across the registered instances in its Availability Zone only.

Question 5

(Advanced Load Balancers) What are the benefits of Cross Load Balancing?

Answer 5

Cross-zone load balancing reduces the need to maintain equivalent numbers of instances in each enabled Availability Zone, and improves your application’s ability to handle the loss of one or more instances. However, we still recommend that you maintain approximately equivalent numbers of instances in each enabled Availability Zone for higher fault tolerance.

Question 6

(Advanced Load Balancers) What are Path Patterns?

Answer 6

You can create a listner with rules to forward requests based on the URL path. This is known as path-based routing. If you are running microservices, you can route traffic to multiple back-end services using path-based routing. For example, you can route general requests to one target group and requests to render images to another target group.

Question 7

What are the Advanced Load Balancer Exam Tips?

Answer 7

1. Sticky Sessions enable your users to stick to the same EC2 instance. Can be useful if you’re storing information locally to that instance.
2. Cross Zone Load Balancing enables you to load balance across multiple AZs.
3. Path Patterns allow you to direct traffic to different EC2 instances based on the URL contained in the request.