"what does the dog actually do if it catches it?"

Author achieved the senior role, but is unsure what comes next.

First of all, congratulations. As somebody that also achieved the senior developer title within the first three years of being hired out of University, mostly by luck: Yay money, but I wasn't a senior engineer really for another five years. For me, I needed to see the long term effects of the changes that I'd made and the software I had written to really understand the difference between cargo cult behaviour and what really mattered for the business I was working for.