The most challenging work you did recently

I have to be honest here, I work on a product(small distributed system) that impacts millions of people directly, a very fast paced environment which is totally feature driven. It's obviously domain centric because I work for PayPal and majority of the problems I solve is with money movement. It's highly critical and challenging because of the amount of work and context switching needed. Recently, I have started to interview and I realized though I work hard, it's not actually technically charging or any scalability challenge that i can boast about in an interview. I haven't solved any distributed problem because my product doesn't get billions of requests per day. Mostly in millions. I just use the open source DBs, messaging queues, model the feature e.t.c which for me is not challenging(or am I wrong?)Also, majority of the scalability challenges are solved by an ops team and there are proven architectural designs that can be reused for a new feature. Given this, how do I defend myself in interviews with companies which do get billions of requests per day? Do people esp those with < 7 years of experience get to solve any scalability challenge? Aren't there already proven designs in those companies as well? I want to understand if I got myself wrong in career path. TC : 250K YOE : 6