ELB

Elastic Load Balancing

What is load balancing?

• Load balancers are servers that forward internet traffic to multiple servers (EC2 Instances) downstream.

Why use a load balancer?

• 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 on your instances

• Provide SSL termination (HTTPS) for your websites

• High availability across zones

Why use an Elastic Load Balancer?

• An ELB (Elastic Load Balancer) is a managed load balancer

• AWS guarantees that it will be working

• AWS takes care of upgrades, maintenance, and high availability

• AWS provides only a few configuration knobs

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

• 4 kinds of load balancers offered by AWS:

• Application Load Balancer (HTTP / HTTPS only) – Layer 7

• Network Load Balancer (ultra-high performance, allows for TCP) – Layer 4

• Gateway Load Balancer – Layer 3

• Classic Load Balancer (retired in 2023) – Layers 4 & 7