Scalability

Question 1

How to ensure horizontal scaling?

Answer 1

• auto scaling group

- load balancer

Question 2

How to ensure vertical scaling?

Answer 2

use more powerful ec2 instances

Question 3

How to ensure high availability

Answer 3

• auto scaling group multi AZ

- load balancer multi AZ

Question 4

What are the advantages of load balancers?

Answer 4

• spread load between instances
• expose a single dns to the internet
• provide https for websites
• do health checks for instances
• handle failures of ec2 instances

Question 5

Why use elastic load balancer?

Answer 5

• managed by aws
• less effort
• integration with many aws offerings

Question 6

What load balancers are available?

Answer 6

• classic load balancer
• application load balancer
• network load balancer
• gateway load balancer

Question 7

How can load balancers improve security of ec2 instance?

Answer 7

Through security groups.

• The sg of the load balancer can be opened to the internet.
• The sg of the ec2 instances can be restricted to only let traffic in from the load balancer

Question 8

How can an application load route traffic to different target groups?

Answer 8

• Based on path in URL
• Based on hostname in URL
• Based on Query String, Headers

You would need one classic load balancer for each application.

Question 9

What can an application load balancer target group consist of?

Answer 9

• ec2 instances
• ecs
• lambda functions
• ecs

Question 10

When do you need network load balancer and what does it do?

Answer 10

• for very high traffic and low latency balancing

- it forwards the traffic at the protocol layer

Question 11

How can you make sure a user does not use its session data?

Answer 11

By using sticky sessions using cookies

Question 12

How can you secure the connection using load balancers?

Answer 12

• using a ssl/tls certificate

- certificates can be managed through aws certificate manager

Question 13

How can you react to a decreasing or increasing load using a load balancer?

Answer 13

attach a load balancer to an auto scaling group

Question 14

What are the available scaling policies?

Answer 14

-Dynamic ScalingPolicies
-Target Tracking Scaling (e.g. CPU to stay around 40%)
-Simple Scaling (When a CloudWatch alarm is triggered (example CPU > 70%), then add 2 units
• When a CloudWatch alarm is triggered (example CPU < 30%), then remove 1)

 - Scheduled Actions - Predictive Scaling

Question 15

What are good metrics to scale on?

Answer 15

• CPU utilization
• Request count per target
• any other custom cloudwatch metric

Question 16

How can you perform actions on auto scaling events?

Answer 16

-through lifecycle hooks