AWS Elastic Load Balancer- two web applications in cluster in different autoscaled groups- one load balancer or two?

Question

I'm wondering what the recommend practice would be in this scenario.

If I have two web applications on the same VPC network (essentially in the same cluster) in two different autoscaled groups, would it be possible to use a single Elastic Load Balancer (Application Load Balancer) to send traffic to both applications. And if so, would this been the normal practice, or would two load balancers (one for each application) generally be used? If both methods are possible, are there any pros or cons to each of these methods?

Answer 1

I haven't used ALBs myself, but I have reasonable AWS knowledge and qualifications, so keep that in mind when you read this answer.

The ALB supports host based routing and multiple domains on https using SNI so you can terminate multiple domains on an ALB. Because of this I believe an ALB can do what you want.

I personally would use the same ALB for multiple applications unless it caused some kind of a problem or increased complexity too much. They're not that expensive, but they're not free, so I'd do it to keep costs down.

Others might have good reasons this isn't practical / correct, but my initial view is what you're trying to do is reasonable. Doing a prototype should be fairly quick and easy.