There are other drugs in the pipeline that have a faster onset of action than what is currently available, including GLYX-13 and NSI-189. I have taken NSI-189 and I can confirm that it works fast.
That said, I did find ketamine to be an extremely effective anti depressant with the primary effects being immediately noticeable and positive. I currently re-dose on ketamine every couple months and take bupropion daily--between all of these I've been able to greatly reduce fairly severe depression that went untreated and worsened over a 10+ yr period.