An application consists of the following architecture:
a. EC2 Instances in multiple AZ’s behind an ELB
b. EC2 Instances are launched via an Auto Scaling Group.
c.There is one NAT instance to download the updates from the Internet.
What is a bottleneck in the architecture based on the availability?

Answer options:

A.The EC2 Instances
B.The ELB
C.The NAT Instance
D.The Auto Scaling Group

Correct Answer – C
Since there is only one NAT instance, this is a bottleneck in the architecture. For high availability, launch NAT instances in multiple Available Zones and make them part of an Auto Scaling Group.
For more information on NAT Instances, please visit the following URL:
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_NAT_Instance.html
Note:
NAT Gateway is a better choice than NAT instance as NAT Gateway is highly available. If you`re already using a NAT instance, you can replace it with a NAT gateway.