What is a key weakness of simple modulo hashing when cluster size changes?

What is a key weakness of simple modulo hashing when cluster size changes?

• A. It causes most keys to remap to different nodes, requiring massive data migration.
• B. It remains stable and requires no migration.
• C. It uses a hash ring to determine mappings.
• D. It prevents hot spots from forming.

Answer: (A)

Simple modulo hashing assigns a key to a node by hashing the key and taking the remainder modulo the number of nodes. The weakness shows up when the cluster size changes: the modulus changes for nearly all keys, so most keys end up mapping to different nodes and you must migrate a large amount of data. That makes it very brittle in dynamic environments. In contrast, using a hash ring (consistent hashing) minimizes remapping when nodes join or leave, avoiding massive data movement. Also, simple modulo hashing doesn’t inherently prevent hot spots; if key distribution is uneven, some nodes can become overloaded.

Simple modulo hashing assigns a key to a node by hashing the key and taking the remainder modulo the number of nodes. The weakness shows up when the cluster size changes: the modulus changes for nearly all keys, so most keys end up mapping to different nodes and you must migrate a large amount of data. That makes it very brittle in dynamic environments. In contrast, using a hash ring (consistent hashing) minimizes remapping when nodes join or leave, avoiding massive data movement. Also, simple modulo hashing doesn’t inherently prevent hot spots; if key distribution is uneven, some nodes can become overloaded.