Senior Software Engineer - React Native

At Underdog, we make sports more fun. Our thesis is simple: build the best products and we’ll build the biggest company in the space, because there’s so much more to be built for sports fans. We’re just over five years in, and we’re one of the fastest-growing sports companies ever, most recently valued at $1.3B. And it’s still the early days. We’ve built and scaled multiple games and products across fantasy sports, sports betting, and prediction markets, all united in one seamless, simple, easy to use, intuitive and fun app. Underdog isn’t for everyone. One of our core values is give a sh*t. The people who win here are the ones who care, push, and perform. If that’s you, come join us. Winning as an Underdog is more fun. About the role We're looking for a Senior Software Engineer who specializes in React Native to help us build the core betting experience, from the moment a customer builds a slip through submission, confirmation, and settlement. Our work spans full stack in Ruby, iOS, Android, and Web products, and you'll bring deep React Native expertise to that mix, to make sure the experience holds up to a high bar for speed and reliability at scale. This means owning cross-cutting problems that touch multiple platforms, driving design decisions that hold up under real production traffic, and closing the gap between how a feature is supposed to work and how it actually behaves once it ships. You'll dig into the trickiest bugs and edge cases in the betting experience, help raise the bar for what "done" looks like across the client, and coach other engineers along the way so the patterns you introduce actually stick. Build and scale core parts of the mobile and web apps in React Native; entry building, review, placement, and tracking. The whole lifecycle. Investigate and resolve critical issues in the React Native client, and put guardrails in place so they don't recur. Lead design reviews for initiatives that cut across iOS, Android React Native clients, calling out trade-offs, risks, and failure modes before they become incidents.