Samsung 9910 has a 1:1 TB:GB cache size of LPDDR4X memory. I won't pretend to understand the magic NVMe drives possess, but if you got a 4TB or 8TB 9910, could you not in theory pull in all of the data you require to cache?
I would assume, and it might be a poor assumption, that NVMe controllers don't pull in files, but rather blocks, so even if you had a database that exceeded cache size, in theory if the active blocks of that database did not exceed cache size, it could be "indefinitely" cached for a read-only pattern.
The DRAM on a SSD like that isn't for caching user data, it's for caching the drive's metadata about which logical blocks (as seen by the OS) correspond to which physical locations in the flash memory.
I would assume, and it might be a poor assumption, that NVMe controllers don't pull in files, but rather blocks, so even if you had a database that exceeded cache size, in theory if the active blocks of that database did not exceed cache size, it could be "indefinitely" cached for a read-only pattern.