You have identifiers for several root entities in Cloud Datastore and want to minimize datastore operation overhead when retrieving them. What should you do?

A batch get operation is the most efficient way to retrieve multiple entities by their keys in Cloud Datastore. By constructing a Key for each root entity and using a batch get, you minimize network round trips and Datastore operation overhead compared to individual get operations. Individual get operations would incur a separate network call for each entity, increasing latency and cost. Using query filters, even in a batch query, is less efficient than a direct key lookup because queries involve indexing and potentially scanning, which are more resource-intensive than retrieving by a known key. Multiple queries per entity using filters would be the least efficient option.