Which of the following is NOT a sharding method?

The selection of "Grouped" as the option that is NOT a sharding method is accurate because the recognized methods of sharding in MongoDB are primarily Range, Hash, and Zoned.

Range-based sharding divides data based on specified ranges of the shard key, distributing documents into shards based on the values of the shard key. This method is effective for workloads with a predictable pattern of access since it allows for more straightforward routing of queries based on ranges.

Hash-based sharding distributes documents by applying a hash function to the shard key. This ensures that the data is spread evenly across shards, helping to prevent hotspots and maintain balanced performance across the database.

Zoned sharding is an evolution of range sharding that allows for more control over how data is distributed in relation to specific zones, such as geographic regions. This method helps ensure that data relevant to users in a certain region is stored on the same shard, improving query efficiency.

In contrast, "Grouped" is not an established sharding technique within MongoDB. MongoDB does not utilize grouping as a strategy for distributing data across different shards, which is why it stands out as the correct answer to this question.