ELB & Auto Scaling Group

Question 1

What are the servers that forward internet traffic to multiple servers (EC2 Instances) downstream called?

Answer 1

Elastic load balancers

Question 2

Why use a load balancer?

Answer 2

• Spread load across multiple downstream instances
• Expose a single point of access (DNS) to your application
• Seamlessly handle failures of downstream instances
• Do regular health checks to your instances
• Provide SSL termination (HTTPS) for your websites
• High availability across zones

Question 3

Why should you use an elastic load balancer?

Answer 3

• An ELB (Elastic Load Balancer) is a managed load balancer
• AWS guarantees that it will be working
• AWS takes care of upgrades, maintenance, high availability
• AWS provides only a few configuration knobs

It costs less to setup your own load balancer but it will be a lot more effort on your end (maintenance, integrations)

Question 4

What are the kinds of load balancers offered by AWS?

Answer 4

• Application Load Balancer (HTTP / HTTPS only) – Layer 7
• Network Load Balancer (ultra-high performance, allows for TCP) – Layer 4
• Classic Load Balancer (slowly retiring) – Layer 4 & 7

Question 5

What is the goal of an Auto Scaling Group (ASG) is to:?

Answer 5

• Scale out (add EC2 instances) to match an increased load
• Scale in (remove EC2 instances) to match a decreased load
• Ensure we have a minimum and a maximum number of machines running
• Automatically register new instances to a load balancer
• Replace unhealthy instances