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.).