The XL-FLASH non-volatile memory promises to be almost as fast as the DRAM volatile memory, yet its price should still be in the 3D NAND range. Kioxia claims the latency times are 10 times lower than traditional 3D NAND and the transfer speeds along with the IOPS are considerably improved, especially for small files and random read/write operations.
https://www.notebookcheck.net/Kioxia-and-Western-Digital-present-ultra-high-speed-XL-FLASH-memory-as-an-alternative-to-Intel-Optane.455335.0.html