Horizontal and Vertical Scaling

Question 1

Define vertical scaling

Answer 1

Vertical scaling is to increase the capacity of the server when the load increases - but this will require a reboot.

Question 2

Mention some disadvantages and limitations of vertical scaling:

Answer 2

• Often times vertical scaling can only occur during planned outages - limits how quickly you can react/response to changes by scaling up or down.
• Larger instances also carry a $ premium compared to smaller instances - bigger instance, more expensive
• Instance size is an upper cap on performance.

Question 3

Mention some advantages and limitations of vertical scaling:

Answer 3

• No application modification is needed - Works for all applications, even monoliths (all code in one app)

Question 4

Define horizontal scaling

Answer 4

Horizontal scaling is to add additional capacity when the load increases.

Question 5

What is the main difference between vertical and horizontal scaling?

Answer 5

With horizontal scaling, instead of one running copy of an application, you can have multiple versions running on each server (normally with smaller compute)

Question 6

What is the function of the load balancer in horizontal scaling? Is it required?

Answer 6

This requires a load balancer. When customers try to access an application, the load balancer ensures the servers get equal parts of the load.

Question 7

What are sessions and why are they important in horizontal scaling?

Answer 7

Sessions define the state of your interaction.
With horizontal scaling you might be jumping from instances and therefore is important to track the state of your interaction.

Question 8

What is required for horizontal scaling to work correctly?

Answer 8

It requires the application to support it or to have off-host sessions, meaning that the sessions are not saved or stored in the instance itself (stateless servers) - session data is saved somewhere else.

Question 9

Is there any disruption when scaling up/down with horizontal scaling?

Answer 9

No.

Question 10

Is there a limitation on how much you can scale with horizontal scaling?

Answer 10

No.

Question 11

Mention some of the benefits of using horizontal scaling:

Answer 11

• No disruption when scaling up/down.
• No real limits when scaling.
• More granular.
• Pay less as you can use smaller instances to scale.