Answer: Create a new Cloud SQL for MySQL instance, enable HA, and use the export and import option to migrate your data.

To enable high availability (HA) on an existing Cloud SQL for MySQL instance following Google-recommended practices, you cannot directly patch or modify the existing instance to enable HA. Google Cloud recommends creating a new Cloud SQL for MySQL instance with HA enabled and then migrating the data from the old instance to the new one. Option A suggests using the export and import option to migrate data, which is a supported and recommended method for migrating data between Cloud SQL instances. Option B suggests using Cloud Data Fusion, which is more complex and not the simplest or most direct method for this specific task. Option C is incorrect because the gcloud instances patch command cannot be used to enable HA on an existing instance. Option D is incorrect because shutting down the instance does not enable HA; HA must be configured at the time of instance creation or by creating a new instance with HA enabled and then migrating the data. Therefore, the correct answer is A.

Author: LeetQuiz Editorial Team