introduction to load balancer

 Load balancers are basically servers that forward internet traffic to multiple servers (EC2 instances) down stream.

suppose we have 3 EC2 instances and all the 3 runs same application and  one load balancer.

       

             Similarly if we have 1500 users load balancer will assign 500 user to first EC2 instance,500 users to second EC2 instance and 500 users to third EC2 instance.

Why to use a load balancer?

• Spread load across multiple downstream instances.
• Expose  a single point of access (DNS) to your application.
• Seamlessly handle failures of downstream instances.
• Do regular health checks to your instances.
• Provide SSL termination (HTTPS) for your websites.

Types of load balancer on AWS:

1. Classic Load balancer(V1).
2. Application load balancer(V2 - new generation).
3.  Network load balancer(V2 - newer generation).
   
   it is recommended to use the new the newer / v2 generation load balancers as they provide more features.

You can setup internal (private) or external (public ) ELBs

internal(private): load balancer for applications with in private network.

external( public): load balancer for applications in the public network.
                             ex: web server.