My advice is that you take it to an authorised Apple dealer. Individual keys may need replacing; it is possible that the keyboard may need replacing - you do not know the extent of the problem until someone qualified has been able to identify it.
I had problems with the letter 'a' on my 2013 MBA's keyboard last year - the 'a' had become detached, and kept falling off, despite my attempts to secure it.
When I was home, I took it into an authorised Apple dealer. 'A" was not the only key giving trouble - ironically, the number '1' was also problematic. Anyway, the computer was still under warranty, and I also have Applecare.
While I assumed that the errant keys would be replaced, in fact, the entire keyboard was replaced under Applecare.