Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 230 discussion

See https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-comparison.html

fyi yall in most cases nat instances are a bad thing because their customer managed while nat gateways are AWS Managed. So in this case I already know to get rid of the nat instances the reason its c is because it wants high availability meaning different AZs

Highly available, fault tolerant and automatically scalable=> Autoscaling and Diffrent AZ

Highly available, fault tolerant, and automatically scalable = two NAT gateways in different Availability Zones

Remove the two NAT instances and replace them with two NAT gateways in different Availability Zones

This recommendation ensures high availability and fault tolerance by distributing the NAT gateways across multiple AZs. NAT gateways are managed AWS services that provide scalable and highly available outbound NAT functionality. By deploying NAT gateways in differentAZs, the company can achieve redundancy and avoid a single point of failure. This solution also provides automatic scaling to handle increasing traffic without manual intervention. Option A is incorrect because placing both NAT gateways in the same Availability Zone does not provide fault tolerance. Option B is incorrect because using Auto Scaling groups with Network Load Balancers is not the recommended approach for NAT instances. Option D is incorrect because Spot Instances are not suitable for critical infrastructure components like NAT instances.

HA: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-comparison.html Scalability: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html

Could anybody teach me why the B cannot be correct answer? This solution also seems providing Scalability(Auto Scaling Group), High Availability(different AZ), and Fault Tolerance(NLB & AZ). I honestly think that C is not enough, because each NAT gateway can provide a few scalability, but the bandwidth limit is clearly explained in the document. The C exactly mentioned "two NAT gateways" so the number of NAT is fixed, which will reach its limit soon.

C. If you have resources in multiple Availability Zones and they share one NAT gateway, and if the NAT gateway’s Availability Zone is down, resources in the other Availability Zones lose internet access. To create an Availability Zone-independent architecture, create a NAT gateway in each Availability Zone and configure your routing to ensure that resources use the NAT gateway in the same Availability Zone. https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html#nat-gateway-basics

Replace NAT Instances with Gateway

Correct answer is C