Does it make sense to have an Amazon Elastic Load Balancer with just one EC2 instance?

Question

my question is simple. Does it make sense to have an Amazon Elastic Load Balancer (ELB) with just one EC2 instance?

If I understood right, ELB will switch traffic between EC2 instances. However, I have just one EC2 instance. So, does it make sense?

On the other hand, I´m using Route 53 to route my domain requests example.com, and www.example.com to my ELB, and I don´t see how to redirect directly to my EC2 instance. So, do I need an ELB for routing purposes?

Answer 1

Using an Elastic Load Balancer with a single instance can be useful. It can provide your instance with a front-end to cover for a disaster situation.

For example, if you use an auto-scaling group with min=max=1 instance, with an Elastic Load Balancer, then if your instance is terminated or otherwise fails:

1. auto-scaling will launch a new replacement instance
2. the new instance will appear behind the load balancer
3. your user's traffic will flow to the new instance

This will happen automatically: no need to change DNS, no need to manually re-assign an Elastic IP address.

Later on, if you need to add more horsepower to your application, you can simply increase your min/max values in your autoscaling group without needing to change your DNS structure.

Answer 2

It's much easier to configure your SSL on an ELB than an EC2, just a few clicks in the AWS console. You can even hand pick the SSL protocols and ciphers.

It's also useful that you can associate different security groups to the actual EC2 and the forefront ELB. You can leave the ELB in the DMZ and protect your EC2 from being accessible by public and potentially vulnerable to attacks.