Can I upgrade my 121 GB Flash Storage SSD?
In the past, Apple doesn't upgrade any storage as a rule. This is HDD/SSD across the board. The only exceptions I've known are:


If you have several internal bays and you buy the part (Think Mac Pro with 4 SATA bays or Xserve / Xserve RAID)
You are paying for a service repair and they upgrade you for free to a larger drive. You don't ask for it, but Apple asks if you're OK with a better drive and no one refuses that offer.


You should ask them since it's free to ask and they might say yes one day.

That being said, there are many third party options to upgrade storage - but you need to hire someone else or DIY on that repair.

Everymac has a nice overview of the options and challenges as does OWC.