072 Scalability & Availability

Scalability

App/System can handle greater loads by adapting

Types

• Vertical scalability
• Horizonstal scalability (= elasticity)

Vertical Scalability

• Increasing the size of the instance
• Example) RDS, ElastiCache

Horizontal Scalability

• Increasing the # of instances/systems for your app
• Distributed system

High Availability

• Running your app/system at least 2 data centers (AZ)
• Goal: to survive a data center loss

Passive

• RDS Multi AZ

Active

• horizontal scaling

In EC2

Vertical scaling: increase instance size

Horizontal scaling: increase # of instances

• Auto scaling group
• Load balancer

High availability: run instances for the same app across multi AZ

• Auto scaling group multi AZ
• Load balancer multi AZ