QNAP TS-453D comes with only 4GB of RAM, and if you are going to do RAM intensive tasks like using Containers or Virtual Machines, you will definitely need to upgrade the RAM.
Synology DDR4 RAM has been available in the market for a few years now and it is mainly targeted at businesses.
But with the release of the Synology DiskStation DS20 Plus series for consumers, you can finally get the DDR4 RAM to go along with your new shiny DS920+, DS720+, DS420+, or DS220+.