STT-MRAM is one of the alternatives for current SRAM and NAND flash memory / storage solutions. Intel's current implementation is manufactured on the 22 nm node, and promises faster read/write speeds, better endurance, and long-term data storage at higher temperatures. Its hybrid nature should allow Intel to include it in future Optane products.
https://www.notebookcheck.net/Intel-s-STT-MRAM-ready-for-mass-production-viable-alternative-for-SRAM-and-NAND-flash.410599.0.html