The transition for me came when I started a new job and my first project was to fix a slow batch job. Then I managed to get a second performance improvement project and soon I was the performance guy focusing entirely on performance projects. I really loved it.
Then through side projects targeted at problems I saw at the company, I built valuable tools using new open source tech and I got made tech lead of a new platforms team, solely focused on resolving technical problems and improving the system. Since then I have been an R+D engineer and now starting as a big data developer at the same company.
I am no genius, failed my interviews to get into big tech companies. I am a pretty big fish in a pretty small pond, I am known as one of the best technical guys in the company, which opens many doors and gives me a lot of freedom to move about inside the company and get some of the most interesting technically focused projects.