Amazon Elastic Load Balancing (ELB) is a service provided by AWS that automatically distributes incoming web traffic across multiple Amazon Elastic Compute Cloud (EC2) instances. This can help to improve the availability and scalability of applications, by ensuring that there is enough capacity to handle the incoming traffic and by automatically routing traffic to healthy instances.
There are two types of Elastic Load Balancers:
Application Load Balancer (ALB)
This type of load balancer is best suited for routing HTTP/HTTPS traffic. It can route a client request to one of the available service instances, based on the content of the request. It also supports features such as path-based routing and host-based routing.
Network Load Balancer (NLB)
This type of load balancer is best suited for TCP/UDP traffic, including but not limited to applications that use Transport Layer Security (TLS) termination, real-time streaming, gaming, and other TCP/UDP-based protocols. It routes incoming traffic to instances using a flow-hash algorithm, which ensures that traffic for a given connection is sent to the same instance.
Both types of load balancers can be used to improve the availability and scalability of applications. By distributing incoming traffic across multiple instances, ELB can help to ensure that there is enough capacity to handle the incoming traffic, even if one or more instances fail. Additionally, ELB can automatically route traffic to healthy instances, while automatically detecting and removing unhealthy instances.
AWS also offers Elastic Load Balancer Auto Scaling, which automatically scales the number of instances in an Auto Scaling group in response to incoming traffic. This can help to ensure that there is always enough capacity to handle incoming traffic, while also helping to reduce costs by only running the necessary number of instances.
Overall, Amazon Elastic Load Balancing provides a simple and efficient way to distribute incoming traffic across multiple instances, improving the availability and scalability of applications while also reducing the operational overhead of managing the infrastructure.