Which strategy would address this issue?

Explanations:

Increasing the grace period to 180 seconds and requiring three consecutive 200 responses would delay the instances coming online. This would exacerbate the problem of increased error rates since instances would not be considered healthy until they meet these stricter criteria, prolonging the unavailability period during deployments.

While increasing the grace period to 120 seconds may help, changing the response code requirement from 200 to 204 does not solve the underlying issue of the application not being ready to serve requests. A 204 response indicates no content, which could mislead the health check into thinking the instance is healthy even if it’s not fully functional.

Modifying the deployment script to create a /health-check.php file when the deployment begins may not resolve the problem if the application is not ready to respond correctly at that time. Instances may still be considered healthy before they are fully prepared to handle traffic, potentially leading to increased error rates.

This option effectively addresses the issue by ensuring that the health check only passes once all deployment tasks are complete. By creating the /health-check.php file after the deployment is finished, it guarantees that the health check only verifies the instance’s readiness after the application is fully operational, thus reducing the likelihood of errors for users.