Which distribution technique minimizes data movement when shards are added or removed by placing shards on a virtual ring and assigning each key to the nearest shard clockwise?

Which distribution technique minimizes data movement when shards are added or removed by placing shards on a virtual ring and assigning each key to the nearest shard clockwise?

• A. Range-Based Sharding assigns contiguous ranges of shard key values to specific shards.
• B. Directory-Based Sharding stores shard assignments in a lookup table for flexible movement.
• C. Consistent Hashing arranges shards on a virtual ring and assigns each key to the nearest shard clockwise to minimize data movement.
• D. Hot Spot Problem describes unequal traffic across shards.

Answer: (C)

Consistent hashing. By laying out shards on a virtual ring and mapping each key to the nearest shard clockwise, you create a stable, ring-based partitioning that keeps data movement small when shards are added or removed. When a new shard joins, only the keys that fall between that shard’s position and its predecessor need to move to the new shard; all other keys stay put. When a shard leaves, only the keys on that shard shift to the next one clockwise. This limited data shuffling makes scaling and fault tolerance more efficient. In contrast, range-based sharding ties keys to fixed value ranges, so changing the shard count often requires redistributing large data portions; directory-based sharding relies on a lookup table and doesn’t inherently minimize movement, and hot spots describe uneven traffic rather than how shards are mapped.

Consistent hashing. By laying out shards on a virtual ring and mapping each key to the nearest shard clockwise, you create a stable, ring-based partitioning that keeps data movement small when shards are added or removed. When a new shard joins, only the keys that fall between that shard’s position and its predecessor need to move to the new shard; all other keys stay put. When a shard leaves, only the keys on that shard shift to the next one clockwise. This limited data shuffling makes scaling and fault tolerance more efficient. In contrast, range-based sharding ties keys to fixed value ranges, so changing the shard count often requires redistributing large data portions; directory-based sharding relies on a lookup table and doesn’t inherently minimize movement, and hot spots describe uneven traffic rather than how shards are mapped.