ALB vs NLB: Which AWS load balancer fits your needs?
Choosing the right load balancer is crucial when it comes to optimizing the performance and availability of your applications and workloads. There are several options to choose from, but two of the most popular choices are Amazon Web Services (AWS) Application Load Balancer (ALB), and Network Load Balancer (NLB). Each load balancer type has unique features and capabilities, so choosing the right one for your workload is important.
ALB
The ALB operates on layer 7, which means it inspects the details of every incoming HTTP request. It is designed to route traffic to target groups based on the content of the request and supports HTTP/1.1, HTTP/2, or gRPC. It also provides advanced request routing features, such as support for multiple protocols, path-based routing, and the ability to bind to multiple SSL certificates.
Here is an example of how to create an ALB using AWS CLI:
aws elbv2 create-load-balancer --name my-alb --subnets subnet-12345678 subnet-87654321 --security-groups sg-12345678 --type application
NLB
The NLB, on the other hand, works on layer 4 and only cares about forwarding the incoming TCP or UDP connection to a target. It does not inspect an incoming HTTP request. It is designed to route traffic to target groups based on IP address and TCP port and supports any TCP-based protocol. It provides ultra-low latencies and can handle high levels of traffic.
Here is an example of how to create an NLB using AWS CLI:
aws elbv2 create-load-balancer --name my-nlb --subnets subnet-12345678 subnet-87654321 --security-groups sg-12345678 --type network
Which one to choose?
When deciding between an ALB and an NLB, choose the ALB unless one of the following applies to your scenario:
Clients connect via UDP or non-HTTP
You want to use HTTP/3 (NLB is currently the only choice)
You need to use features of the NLB that the ALB does not provide
It's worth noting that it's not a big deal to switch from an ALB to an NLB or vice versa, as the components are the same. However, you can only do so if you do not use any features of the ALB that the NLB does not provide.
When in doubt, choose the ALB. It comes with a lot of built-in features and is easier to use than the NLB. The NLB comes with a few rough edges and requires more experience and care.