Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 306 discussion

Reasons: • Launching instances within a single AZ and using a cluster placement group provides the lowest network latency and highest bandwidth between instances. This maximizes performance for an in-memory database and high-throughput application. • Communications between instances in the same AZ and placement group are free, minimizing data transfer charges. Inter-AZ and public IP traffic can incur charges. • A cluster placement group enables the instances to be placed close together within the AZ, allowing the high network throughput required. Partition groups span AZs, reducing bandwidth. • Auto Scaling across zones could launch instances in AZs that increase data transfer charges. It may reduce network throughput, impacting performance.

Apart from the fact that BCD distribute the instances across AZ which is bad for inter-node network latency, I think the following article is really useful in understanding A: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html

• Launching instances within a single AZ and using a cluster placement group provides the lowest network latency and highest bandwidth between instances. This maximizes performance for an in-memory database and high-throughput application. • Communications between instances in the same AZ and placement group are free, minimizing data transfer charges. Inter-AZ and public IP traffic can incur charges. • A cluster placement group enables the instances to be placed close together within the AZ, allowing the high network throughput required. Partition groups span AZs, reducing bandwidth.

Cluster placement group packs instances close together inside an Availability Zone. This strategy enables workloads to achieve the low-latency network performance.

Launch all EC2 instances in the same Availability Zone within the same AWS Region. Specify a placement group with cluster strategy when launching EC2 instances

Cluster - have low latency if its in same AZ and same region so Answer is "A"

Answer would be A - As part of selecting all the EC2 instances in the same availability zone, they all will be within the same DC and logically the latency will be very less as compared to the other Availability Zones.. As all the autoscaling nodes will also be on the same availability zones, (as per Placement groups with Cluster mode), this would provide the low-latency network performance Reference is below: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html

A - Low latency, high net throughput

A placement group is a logical grouping of instances within a single Availability Zone, and it provides low-latency network connectivity between instances. By launching all EC2 instances in the same Availability Zone and specifying a placement group with cluster strategy, the application can take advantage of the high network throughput and low latency network connectivity that placement groups provide.

Cluster placement groups improves throughput between the instances which means less EC2 instances would be needed thus reducing costs.

A because Specify a placement group

It is option A: To achieve low latency, high throughput, and cost-effectiveness, the optimal solution is to launch EC2 instances as a placement group with the cluster strategy within the same Availability Zone.

Why not C?

Answer is A - Clustering

A : Cluster placement group