KeyDB implements multiple threading with spin-locks that protect a global shared data structure.

Dragonfly is built upon shared-nothing architecture where each thread manages its own slice of data, hence no need for classical locks and no contention under high load. It still provides atomicity guarantees but allows multiple transactions to progress independently as long as they do not need exlusive access to the same keys. So basically different approaches to the same promise - scale. Also different trade-offs. Shared-nothing approach has less contention and more flexible transaction framework but inhibits a slightly higher 50%th percentile latency (order of 30usec).

KeyDB is a fork of Redis, whereas Dragonfly introduces a brand-new architecture, crafted from the ground up utilizing a share nothing, multi-threaded design. It implements both Redis and memcached APIs