MongoDB query: select all documents with latest timestamp

Working with Data Java Frameworks
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6

Wait, I just noticed that this returns what I need:

    Aggregation aggregation = newAggregation(
        group("$key")
            .max("$timestamp").as("timestamp")
            .first("$value").as("value")
    );

The only difference is that “key” is called “_id” in the output. Not sure if one can rename it.

Is this an inefficient way of solving the problem?