Principal Engineer, Card Readers Team

Toast creates technology to help restaurants and local businesses succeed in a digital world, helping business owners operate, increase sales, engage customers, and keep employees happy. As a Principal Engineer on the Card Readers team, you will be a technical leader responsible for designing, developing, and maintaining our POS payment integrations. You will work closely with hardware SDKs, the core POS application team, and other cross-functional stakeholders to drive technical decisions and define the target architecture for our payment solutions. Your expertise in high-throughput asynchronous JVM solutions, coupled with a deep understanding of mission-critical transactional processing, will be crucial in delivering robust and scalable solutions. A day in the life (Responsibilities) Develop and execute technical strategies to solve complex business challenges, leveraging data and customer insights to prioritize impactful improvements. Establish guiding technical and delivery principles that influence engineering practices across the broader engineering organization. Architect, design, and develop robust, high-performance applications using Kotlin, optimized for security, speed, availability, and reliability. Raise the bar as a high-throughput, hands-on code contributor modeling high standards. Lead agile development processes, including sprint planning, daily stand-ups, and retrospectives. Mentor and guide engineers, fostering a culture of continuous improvement, inclusivity, and engineering excellence. Build and maintain strong partnerships across lines of business, aligning technical solutions with strategic objectives. Leverage cutting edge AI tools to enhance your development workflow, improve velocity, and help pioneer new approaches to building - contributing to a culture of innovation and productivity across the team. What you'll need to thrive (Requirements) Demonstrated ability to lead large, cross-team platform initiatives, setting technical direction beyond a single team or service Expert-level proficiency in Kotlin, Java, and/or JVM languages, including high-scale successes with multi-threading/concurrency (deep experience with coroutines a plus) Fluency with card payments, particularly EMV standards and technology. Experience working in a large (Android) project/codebase, architecting for clear domain boundaries, modularity, reusability, and testability Track record of complex and robust SDK integrations completed successfully Expertise in security and key management best practices Experience designing public APIs for hassle-free consumption Expertise in observability, monitoring, and alerting for complex user-device interactions Strong skills in mentoring a team of developers on best practices Openness and enthusiasm for AI tooling to enhance R&D productivity Excellent communication, collaboration, and problem-solving skills that lead others by example Nice to have: Low-level hardware/device integration experience, and/or experience with hardware abstraction Experience working with third-party payment gateways, in-app purchases, POS integrations, or other aspects of fintech AI at Toast At Toast, one of our company values is that we're hungry to build and learn. We believe learning new AI tools empowers us to build for our customers faster, more independently, and with higher quality. We provide these tools across all disciplines, from Engineering and Product to Sales and Support, and are inspired by how our Toasters are already driving real value with them. The people who thrive here are those who embrace changes that let us build more for our customers; it’s a core part of our culture. Our Total Rewards Philosophy We strive to provide competitive compensation and benefits programs that help to attract, retain, and motivate the best and brightest people in our industry. Our total rewards package goes beyond great earnings potential and provides the means to a healthy lifestyle with the flexibility to meet Toas