65. High Availability, Scalability, Elasticity

Scalability

an application / system can handle greater loads by adapting; ability to accommodate a larger load by making the hardware stronger (scale up), or by adding nodes (scale out)

Vertical Scalability

increasing the size of the instance

Horizontal Scalability

increasing the number of instances / systems for your application

Vertical scalability is very common for

non-distributed systems, such as a database.

What is the limit to how much you can vertically scale

Hardware limit

Horizontal scaling implies

distributed systems

Horizontal scalability is very common for

web applications / modern applications

High Availability

running your application / system in at least 2 Availability Zones

The goal of high availability is

to survive a data center loss (disaster)

Elasticity

there will be some “auto-scaling” so that the system can scale based on the load. This is “cloud-friendly”: pay-per-use, match demand, optimize costs

Agility

new IT resources are only a click away, which means that you reduce the time to make those resources available to your developers from weeks to just minutes.