Sorry, missed your second question. Redis is using fork-based save for snapshotting and full replica sync. This means that memory pages are duplicated on write. That consumes more memory than DF implementation that implements algorithmic point-in-time snapshotting. In addition DF was designed to use less overhead memory in its keys table. As for the why, you can read about it here: https://github.com/dragonflydb/dragonfly#background