Senior Software Engineer - React Native

At Underdog, we make sports more fun. Our thesis is simple: build the best product for sports fans and we will win the space. Founded in 2020, we're one of the fastest-growing sports companies ever, and there’s still so much left to do. We've built and scaled products across fantasy sports, sports betting, and prediction markets, all united in one app that’s seamless, intuitive, and actually fun to use. 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. We’re remote-first by design, but highly collaborative with regular in-person gatherings that help teams build, iterate, and move fast together. Got that dog in you? Join us. After all, winning as an Underdog is more fun. What you'll do: 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. Partner with backend, product, and design on entry placement, entry confirmation, slip changes and errors, and bet history to keep the experience fast and consistent Turn ambiguous, cross-team goals into concrete plans with milestones and clear owners Use data like product analytics, error dashboards, and session data to validate that fixes actually land and to catch regressions early Coach other engineers on design reasoning and ownership, and create reusable patterns that other teams adopt Anticipate and mitigate risks in shared systems before they impact other teams or customers Who you are: 7+ years of professional software engineering experience, with meaningful time spent in React Native and a solid grasp of the native iOS/Android layers underneath it A track record of solving cross-cutting or ambiguous problems that span multiple services, teams, or platforms; not just staying in your lane Experience leading technical initiatives (performance work, reliability improvements, developer velocity) with measurable before/after impact Comfort turning unclear, high-level goals into an executable plan with milestones and owners that other teams actually align on A collaborative, coaching mindset; you make other engineers better through review and design discussion, not just your own output Strong written and verbal communication; you can make a technical trade-off legible to product, design, and other engineering teams Experience with mobile app performance, testability, and shipping reliable features at scale Bonus points if you have: Background in sports, fantasy, or gaming Experience working on wagering, betting, or other high-stakes transactional flows Familiarity with Amplitude, Datadog, or similar tools for instrumenting and monitoring client-side behavior Our target starting base salary range for this position is between $150,000 and $220,000, plus target eq…