Graduating from SaaS, Crossing the Sea: In-House Rails Behind 2,000 Unstaffed Gyms, and How AI Shifted the Build-vs-Buy Break-Even Point

chocoZAP runs 20,000 in-store cameras, digital signage, and a reservation system. All three started on SaaS and have since been replaced with in-house Rails systems. It all started with a lesson we learned when we relied on outsourcing. This talk shares, with real numbers, five years of bringing development in-house with a team that is half new graduates, and how the arrival of AI agents moved the break-even point of Build vs. Buy. We will also explain why we keep choosing Ruby in the AI era, and how our in-house platform has begun crossing the sea to Hong Kong and Taiwan.