NLB layer 4 – TCP includes port 80 so it can load balance web pages correct? What are other use cases? Is NLB more expensive to implement than ALB?

Hello, 
You’re right, you can loadbalance TCP on port 80 with NLB , but it would be inefficient. With NLB you cannot use application layer feature such as redirection, path filtering etc … like ALB. 
Usually, NLB are useful to manage other kind of traffic and have better performance than ALB.

Hi, 

If I can add something here which may be useful. Think also about the difference between the NLB and ALB from the perspective of the IP packets it receives.

The NLB takes a decision at layer 4 and only needs to read the IP+TCP headers to take a load balancing decision.

The ALB on the other hand makes decisions based on the application layer data and therefore needs to read and understand multiple packets before a load balancing decision can be made.

The choice between the 2 solutions may need to take the above into consideration. NLB implies less complexity and greater throughput.

Pricing seems similar between the 2: https://aws.amazon.com/elasticloadbalancing/pricing/

Hope this is useful.

Paul