Which combination of steps will meet this requirement with the LEAST amount of operational overhead?

Explanations:

Creating an Amazon S3 bucket to host static webpages is a straightforward way to provide a custom error page. This option requires minimal operational overhead, as S3 can serve static content reliably without needing additional infrastructure.

Creating a CloudWatch alarm and using a Lambda function to modify the ALB’s forwarding rules adds unnecessary complexity and operational overhead. This approach would require more management and maintenance than simply hosting custom error pages on S3.

Modifying Route 53 records to add health checks and set fallback targets introduces additional operational complexity. This method does not provide a direct solution for customizing error pages and would require ongoing management of DNS records and health checks.

Similar to option B, this involves creating CloudWatch alarms and modifying ALB rules through Lambda, which increases complexity and operational overhead without directly addressing the requirement for a custom error page.

Configuring a CloudFront custom error page allows for serving a custom error page with minimal operational overhead. This option leverages existing CloudFront configurations and can directly handle errors from the ALB without needing to change the backend infrastructure.