Fullstack Staff Engineer

About DEUNA 🧡 DEUNA is a rapidly growing startup revolutionizing global commerce with ATHIA, our AI-powered orchestration and payments platform that helps large enterprises boost approval rates, reduce costs, and unlock new revenue. Built by the team behind DEUNA—the fastest-growing Commerce OS in Latin America—ATHIA combines payment intelligence, checkout optimization, and data orchestration in one powerful solution. With deep integrations across 300+ PSPs and alternative payment methods, and over 20% of Mexico’s digital economy running through our platform, we simplify global payments through a single integration and centralized reconciliation. We are a rapidly growing startup expanding into the U.S. to meet the urgent needs of large retailers, marketplaces, airlines, and QSRs. Join us to shape the future of payments! 🚀 Visit https://www.deuna.com/ to learn more about us! Role Overview We are looking for a Staff Software Engineer – Fullstack to act as a senior technical leader across our engineering organization. This is a high-impact individual contributor role, focused on driving architecture, setting technical direction, and solving complex, cross-team challenges. You will partner closely with Engineering, Product, and leadership to ensure our systems scale reliably as the business grows. This role is not focused on people management — instead, you will operate as a technical authority and multiplier, influencing multiple teams and raising the overall engineering bar. What You’ll Do Technical Leadership & Architecture Own and evolve the architecture of critical fullstack systems across frontend and backend. Lead the design of scalable, high-performance, and resilient distributed systems. Set and uphold engineering standards, best practices, and design principles. Drive alignment across teams on architectural decisions and technical direction. Hands-On Engineering Contribute to high-impact areas of the codebase. Write clean, maintainable, production-grade code. Lead complex refactors and performance optimization efforts. Conduct in-depth code reviews and mentor engineers through technical guidance. Cross-Team Impact Partner with Product and Engineering leaders to evaluate trade-offs across scalability, performance, cost, and security. Design APIs, data models, and system interactions that support long-term growth. Guide teams on handling edge cases, failure scenarios, and observability. Technical Strategy & Innovation Identify system bottlenecks and drive scalable solutions. Influence long-term technical strategy and roadmap. Evaluate and introduce new technologies where they add meaningful value. Improve monitoring, instrumentation, and system reliability practices. What We’re Looking For Proven experience as a Staff, Principal, or Senior Software Engineer in fullstack environments. Strong frontend expertise with: React Next.js TypeScript Strong backend experience with: Golang and/or Python Deep experience designing distributed systems and scalable APIs. Strong fundamentals in: Data structures and algorithms System design and architecture Design patterns and trade-offs Hands-on experience with AWS and cloud-native architectures. Experience with SQL and NoSQL databases. Strong debugging, performance optimization, and refactoring skills. Excellent communication skills, with the ability to influence technical decisions. Fluent or native English (Spanish is a plus). Nice to Have Experience in payments, fintech, e-commerce, or transaction-heavy platforms. Experience building high-availability, low-latency systems. Familiarity with regulated environments (PCI-DSS, financial systems, etc.).