Steemit Inc / @steemitblog have claimed that full RPC nodes require 32 GB to 64 GB of RAM post RocksDB/AppBase/0.19.1x, and that the recommended configuration is shared-memory on NVMe/Optane disks even for full nodes. RocksDB is repeatedly heralded as "on-disk" solution. (Source; and Source)
I'm not aware of this being verified independently, however. Either way, for 0.19.10+ the "512 GB RAM" requirements are questionable, at best; obsolete most likely. I have no reason to believe Steemit Inc. are lying.