Why the picture is showing only 2 AZs

[VG-AWS]

18. QUESTION

Category: CSAP – Design for New Solutions

You are the CTO of your co-founded startup where you are building an innovative AI-powered traffic monitoring portal using AWS as its cloud infrastructure. As the system would be used in the entire city, it should be highly available and fault-tolerant to avoid unnecessary downtime.

Which of the following options is the MOST suitable architecture that you should implement?

[TutorialsDojo-Support]

Hello vipul-gupta,

Thank you for your feedback.

“You are the CTO of your co-founded startup where you are building an innovative AI-powered traffic monitoring portal using AWS as its cloud infrastructure. As the system would be used in the entire city, it should be highly available and fault-tolerant to avoid unnecessary downtime.

Which of the following options is the MOST suitable architecture that you should implement?”

Launch an Auto Scaling group of EC2 instances on three Availability Zones. Attach an application load balancer to the Auto Scaling Group. Use an Amazon Aurora Multi-Master as the database tier. Use Route 53 and create alias record to point to the ELB. Use ElastiCache for the database caching of the portal.

The answer says that we launch your instance on 3 Availability Zone while the diagram shows only Availability Zones. The diagram was taken from AWS documentation, and this is for reference only.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/images/tutorial_as_elb_architecture.png

The concept of fault-tolerant implied here is to always spread your EC2 instances in at least 2 (or more) Availability Zones. 2 Availability Zones on AWS will rarely go down. When using multi-AZ setups, even if 1 Availability Zone is down, your application is still available.

The choice “Launch an Auto Scaling group of EC2 instances on two Availability Zones. Attach an application load balancer to the Auto Scaling Group. Use a MySQL RDS instance with Multi-AZ deployments configuration. Use Route 53 and create an A record to point to the ELB.” is incorrect. The ELB does not have an A-record that you can use for Route53. You should use Alias-record for ELBs DNS names on Route53.

Regards,

Kenneth Samonte @ Tutorials Dojo

• This reply was modified 3 years, 11 months ago by  TutorialsDojo-Support.

[VG-AWS]

So, if I get it right. 2 AZs should be fine. There is no need for 3 AZs configuration if “A” record was not an issue.

[TutorialsDojo-Support]

Yes, 2 AZs is fine too. The ‘A-record’ on Route 53, made this choice wrong.

Regards,

Kenneth Samonte @ Tutorials Dojo