* Cluster Placement Group: This type of placement group is designed to provide low-latency network performance and high throughput by grouping instances within a single Availability Zone. It is ideal for applications that require tightly coupled node-to-node communication.
* Configuration:
* When launching EC2 instances, specify the option to launch them in a cluster placement group.
* This ensures that the instances are physically located close to each other, reducing latency and increasing network throughput.
* Benefits:
* Low-Latency Communication: Instances in a cluster placement group benefit from enhanced networking capabilities, enabling low-latency communication.
* High Network Throughput: The network performance within a cluster placement group is optimized for high throughput, which is essential for HPC workloads.
References:
* Placement Groups
* High Performance Computing on AWS

Instances in a private subnet cannot directly reach the internet because they do not have public IP addresses and the private subnet route table typically does not send 0.0.0.0/0 traffic to an internet gateway. However, these instances still need outbound-only internet access to download patches and updates while remaining inaccessible from the internet. The standard AWS design to achieve this is a NAT gateway deployed in a public subnet.
Option C is required because a NAT gateway must reside in a public subnet that has a route to the internet gateway. This allows the NAT gateway to forward outbound traffic from private instances to the internet and return responses, without allowing inbound connections initiated from the internet to those instances.
Option A is required because a NAT gateway uses an Elastic IP address to represent its public-facing identity on the internet. Without an Elastic IP, the NAT gateway cannot communicate with internet endpoints. The Elastic IP is associated with the NAT gateway, not with the internet gateway.
Option B is required because the private subnet needs a route for 0.0.0.0/0 (default route) that targets the NAT gateway. This ensures that outbound internet-bound traffic from the private instances is sent to the NAT gateway rather than being dropped.
Option D is incorrect because a NAT gateway in a private subnet would not have a working route to the internet gateway and would not provide internet egress. Option E is incorrect because the public subnet's default route should point to the internet gateway, not to the NAT gateway. Option F is incorrect because you do not associate Elastic IPs with an internet gateway.
Therefore, A, B, and C correctly implement private subnet outbound internet access while keeping the instances unreachable from the internet.

The lowest-overhead answer isAPI Gateway with direct AWS service integration to DynamoDB PutItem.
DynamoDB's API includes a native PutItem action for writing an item to a table, and API Gateway supports direct AWS service integrations, which lets the web application send requests through an API layer without developers touching DynamoDB directly. This approach is scalable, reusable, and avoids managing Lambda code purely as a pass-through layer. The SQS-based design adds unnecessary queueing for a straightforward write API, and ALB is not the appropriate frontend for invoking DynamoDB actions. Therefore, direct API Gateway service integration is the cleanest design.

Lambda supports mounting an Amazon EFS file system inside your function to store larger dependencies beyond the 250 MB layer quota.
EFS automatically encrypts data in transit using TLS.
"You can configure your Lambda function to mount an Amazon EFS file system, enabling your function to access large amounts of data or large dependencies."
"Amazon EFS automatically encrypts all data at rest and in transit."
- Lambda with Amazon EFS
This is the least operational overhead approach.

Latency-based routing in Amazon Route 53 is designed to route users to the Region that provides the lowest network latency, based on Amazon's measurements of latency between AWS Regions and users' networks.
For applications deployed in multiple Regions, this provides the highest performance experience for global users.
Therefore, creating an A record with a latency routing policy is the correct choice.
Geolocation (Option B) routes based on user location, which may not always correspond to the lowest latency.
Failover (Option C) is for active-passive architectures, not performance optimization.
Geoproximity (Option D) is more complex and focused on directing traffic based on geographic bias rather than measured latency.