Explanation

Correct Answer: A

Why Option A is correct:

1. Minimizes data transfer charges: When EC2 instances are in the same Availability Zone, there are no data transfer charges between them. Data transfer between instances in different Availability Zones incurs charges.
2. Placement group with cluster strategy: This provides low-latency, high-throughput network performance by placing instances close together within a single Availability Zone, which is ideal for latency-sensitive applications like in-memory databases.
3. High network throughput: Cluster placement groups provide high-bandwidth, low-latency networking between instances.
4. Cost-effective: Eliminates cross-AZ data transfer costs while providing optimal performance for the in-memory database.

Why other options are incorrect:

• Option B: Launching instances in different Availability Zones would incur data transfer charges between zones, which contradicts the requirement to minimize data transfer charges.
• Option C: Auto Scaling across different Availability Zones would also incur data transfer charges and doesn't provide the low-latency, high-throughput networking needed for an in-memory database.
• Option D: Similar to option C, this would spread instances across Availability Zones, incurring data transfer charges and not providing optimal network performance for latency-sensitive applications.

Key AWS Concepts:

• Placement Groups: Cluster placement groups pack instances close together inside an Availability Zone to achieve low-latency, high-throughput networking.
• Data Transfer Pricing: Data transfer between Availability Zones is charged, while data transfer within the same Availability Zone is free.
• In-memory databases: Require low latency and high throughput between nodes, making cluster placement groups ideal.
• Network Performance: Cluster placement groups can provide up to 10 Gbps per flow and up to 100 Gbps aggregate bandwidth for supported instance types.