Another comment already mentions this, but I guess a functional data structure would be easiest to maintain, even though there's stuff like this for PMEM such that any data structure would work essentially: https://pmem.io/
This Open Source data store I'm maintaining is storing a huge tree of tries eventually on durable storage, but it's essentially a huge persistent index stored in an append-only file. The last layer of "indirect index pages" stores list of pointers to page fragments, which store the actual records (the list however is bound to a predefinded size). A single read-write trx per resource syncs the new page fragments, which mainly only include the updated or new records plus the paths to the root page to a durable device during a postorder traversal of the in-memory log. The last thing is an atomic update, which sets a new offset to point to the new UberPage, the root of the storage. All pages are only word aligned except for RevisionRootPages, which are aligned to a multiple of 256 bytes. All pages are compressed and might in the future optionally be encrypted.
I guess these byte addressable persistent memory devices are an ideal fit for small sized parallel random reads of potentially tiny page fragments to reconstruct a full page in-memory.
However, I hope they'll eventually achieve a better price in comparison to DRAM and SSDs than Intel Optane DC PMEM current price range.