Keys are hashed using which algorithm by default?

Keys are hashed using which algorithm by default?

• A. murmur2
• B. sha256
• C. md5
• D. crc32

Answer: (A)

Hashing the key for partition selection uses a fast, non-cryptographic hash function, specifically Murmur2. This choice is driven by the need for speed and good distribution rather than security. When a key is present, Kafka hashes the key’s bytes with Murmur2 and then maps that hash value to a partition, typically by taking the modulo with the number of partitions, so identical keys consistently land in the same partition and different keys spread out across partitions. Cryptographic hashes like sha256 or md5 would slow things down without providing additional benefit for partitioning, and crc32, while fast, tends to have a less uniform distribution, which can lead to uneven partition usage.

Hashing the key for partition selection uses a fast, non-cryptographic hash function, specifically Murmur2. This choice is driven by the need for speed and good distribution rather than security. When a key is present, Kafka hashes the key’s bytes with Murmur2 and then maps that hash value to a partition, typically by taking the modulo with the number of partitions, so identical keys consistently land in the same partition and different keys spread out across partitions. Cryptographic hashes like sha256 or md5 would slow things down without providing additional benefit for partitioning, and crc32, while fast, tends to have a less uniform distribution, which can lead to uneven partition usage.