It seems like I love to add as much ram as I can to the devices that I own. I have an Intel Hades Canyon NUC (NUC8i7HVK) with 64GB of RAM, another Intel NUC (NUC8i5BEK) with max out 64GB of ram. A QNAP TS-h886 Enterprise XEON NAS with 128GB ECC Reg Ram.  Also, a DS918+ with 16GB which I used to think it was already maxed out.....Until I see this:

You can find it from your local store for cheaper price, I got mine at ~$100/ea

Wait....what? A 16GB PC3-12800 SODIMM module?

Shut up and take my money

The bad boy: MT16KTF2G64HZ-1G6A1 from Micron


The setup is easy, just pull all the HDD out from the DS918+, pop the RAMs in, and try to boot the devices.

And it boot up successfully:

Synology DS918+ with 32GB RAM


So I have a Synology DS918+ NAS with 32GB ram paired with Intel Celeron J3455 CPU. I honestly don't think the CPU is even powerful enough to consume this amount of RAM.  
Anyway, I am very happy with it, especially when a two years old device can hold up 32GB of system memory. I will possibly gift this device to my sister as her DS216+ replacement and as my remote backup 🤫

I think it is the limit of the DS918+. I will keep updating this post if I find anything interesting in this experiment. Please drop me a message if you want me to test anything, I will try it when I free.