🔸ELB & ASG

Describe about What is ELB and ASG?

What is scalability ?

it mean that an application/system can handle greater loads . There are 2 kind of scalability.

(1) Vertical Scalability

It means increasing the size of the instance (t2.micro -> t2.large) . You can think it like junior dev to be senior dev. (or DB increased hardware spec)

(2) Horizontal Scalability

It means increasing the number of instances for your application. It is the concept of replica. example you scale from 1 instance to 100 instances.

What is high availability ?

It is the stability of our application. The goal of high availability is to survive a data center loss. For greater high availability, you can run your system or application in at least two data centers.

What is load balancing ?

It is a server that forward traffic to multiple servers.

Benefit of load balancer

1. spread load across multiple servers

2. single point of access (DNS)

3. handle failure of instance

4. do health check to instance

5. enforce stickyness cookies

6. high availability across zones

7. separate public traffic from private traffic

ELB (Elastic Load Balancer)

It is a load balancer provided by AWS. AWS gurantees that it wll be working. AWS takes care of upgrades , maintenance and high availability.