Scalability and High Availability : ELB & ASG

Scalability and High Availability :

• Scalability means that application / system can handle greater loads by adapting.

• There are two kinds of scalability

  Vertical scalability

  Horizontal Scalability (= elasticity)

• Scalability is linked but different to high Availability.

Vertical Scalability :

• Vertically scalability means increasing the size of the instance.

• Vertical scalability is very common for non distributed systems, such as a database.

• RDS, ElastiCache are services that can scale vertically.

• There’s usually a limit to how much you can vertically scale ( Hardware limit).

Horizontal Scalability :

• Horizontal scalability means increasing the number of instance / systems for your application.

• Horizontal scaling implies distributed systems.

• This is very common foe web applications / modern application.

• It’s easy to horizontally scale.

High Availability :

• High availability usually goes hand in hand with horizontal scaling.

• High availability means running your application / system in at least 2 data centers ( == Availability zones)

• The goal of high availability is to survive a data center loss.

Conclusion:

Elastic Load Balancing (ELB) and Auto Scaling Groups (ASG) are essential AWS services that work together to ensure high availability and scalability of applications. ELB distributes incoming traffic across multiple targets, improving fault tolerance and responsiveness, while ASG automatically adjusts the number of instances based on demand, maintaining performance and reducing costs. Together, they enable resilient, efficient, and dynamically scalable cloud architectures.