Answer: Run the EC2 instances in a spread placement group.

## Explanation **Correct Answer: A - Run the EC2 instances in a spread placement group.** **Why this is correct:** 1. **Spread Placement Groups** are specifically designed to ensure that instances are placed on distinct underlying hardware to minimize correlated failures. 2. Spread placement groups place each instance in a separate rack, with each rack having its own network and power source. 3. This configuration prevents groups of nodes from sharing the same underlying hardware, which is exactly what the requirement states. 4. Spread placement groups are ideal for applications that require high availability and need to minimize the risk of simultaneous failures. **Why other options are incorrect:** **B. Group the EC2 instances in separate accounts.** - Separate AWS accounts do not control hardware placement. Instances in different accounts can still share underlying hardware in the same AWS region. - This is an organizational/management solution, not a hardware isolation solution. **C. Configure the EC2 instances with dedicated tenancy.** - Dedicated tenancy ensures instances run on single-tenant hardware (dedicated to a single AWS customer), but it doesn't prevent groups of nodes from sharing the same underlying hardware with each other. - All instances with dedicated tenancy could still be placed on the same physical server. - This provides isolation from other AWS customers, not isolation between your own instances. **D. Configure the EC2 instances with shared tenancy.** - Shared tenancy is the default where instances can share hardware with other AWS customers. - This is the opposite of what's needed - it actually increases the likelihood of sharing hardware. **Key AWS Concepts:** - **Spread Placement Groups**: Maximum of 7 instances per Availability Zone, each on distinct hardware. - **Partition Placement Groups**: For large distributed and replicated workloads like HDFS, HBase, and Cassandra. - **Cluster Placement Groups**: For low-latency, high-throughput workloads where instances are placed close together. **Use Case Alignment:** The requirement specifically mentions "prevent groups of nodes from sharing the same underlying hardware," which is the exact purpose of spread placement groups in AWS.

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