Intervals.icu (aka “Intervals RCU”) started as one developer’s side project to analyze torque intervals… and quietly grew into a serious training-analysis platform used by over 120,000 monthly active athletes. In this episode, we sit down with David, the founder, to unpack the full origin story—and what it takes to scale a niche endurance product into something the pro world starts paying attention to. We talk cycling progression (and why he’s chasing an age-group win at the Cape Town Cycle Tour), power-meter accuracy, and how Intervals pulls data from platforms like Garmin and Strava—plus the realities of building on APIs with shifting rules. David also breaks down what “serious” teams care about (kilojoules, durability after 2,000+ kJ, nutrition modeling), why he runs major parts of the infrastructure on real hardware (not just cloud), and how the platform evolved from evenings and early mornings into a full-time business supporting a small team.