Senior / Lead Fullstack Engineer

ABOUT THE ROLE Aplazo is building the financial layer for Latin America's commerce — and we're doing it with a tech team that's small enough to move fast but large enough to tackle genuinely hard problems. We're looking for a Senior or Lead Full Stack Engineer who is equally at home designing a backend service and shipping a polished mobile application. You'll own features end-to-end, work across a modern stack, and be part of a team that ships to millions of users across Mexico. At E2 (Senior), you independently own features and deliver high-quality, production-ready code across the stack. You're the kind of engineer who finishes what they start, writes code others can learn from, and raises quality standards around you. At E3 (Lead), you're the technical anchor of your squad. You own systems, drive architecture decisions, and make the engineers around you meaningfully better. You've been through enough production incidents, rewrites, and tech debt battles to know that the best solution isn't always the most elegant one — it's the one that gets shipped, maintained, and evolved. WHAT YOU'LL BUILD - End-to-end product features — from database schema to API design to the mobile experience users interact with - Internal tools, merchant-facing platforms, and customer-facing mobile flows - Observability from day one — SLOs, alerts, dashboards — so you know when something's broken before users do - Systems designed to be handed off: documented, tested, and legible to the engineer who touches it six months later WHAT YOU'LL DO - Design and implement features across mobile and backend, owning the full surface area - Contribute to (E2) or lead (E3) architecture and design decisions — write proposals, present trade-offs, make calls - Conduct rigorous code reviews — catching correctness issues, security gaps, and opportunities to mentor - Respond to and resolve production incidents, and leave runbooks better than you found them - Use AI tools daily — not as a crutch, but as a force multiplier for speed, testing, and exploration - Help engineers around you grow, especially through pairing, thoughtful feedback, and honest code review (E3) WHAT WE'RE LOOKING FOR TECHNICAL - 3+ years of fullstack experience (5+ for E3), ideally in B2C products - Strong backend skills: Java/Spring as the primary stack; Python or Go a plus - Strong mobile skills: Flutter/Dart — comfortable building real production apps, not just gluing widgets together - Solid experience with APIs (REST, GraphQL), databases (PostgreSQL, MongoDB), and cloud infrastructure (AWS: ECS, Lambda) - Familiarity with microservices and event-driven architectures - Good testing instincts — unit, integration, and enough end-to-end to actually trust your builds - Comfortable with CI/CD pipelines, observability tools (DataDog), and deployment in cloud environments - Awareness of how payments platforms work — the flows, the constraints, the failure modes that matter in a BNPL or fintech product AI FLUENCY We use AI tools as serious development infrastructure, not productivity theater. We expect you to: - Use AI tools (Claude, Copilot, ChatGPT) daily — for coding, debugging, refactoring, and writing tests - Build and share reusable prompts or workflows that raise the team's baseline (E2) - Apply AI strategically for architecture exploration, large-scale refactors, and prototyping (E3) - Think critically about where AI helps and where it misleads — and teach others the difference - Stay current on AI capabilities that are relevant to fintech and development COMMUNICATION - Writes clear technical documentation — the kind that actually gets read - Explains trade-offs to engineers and non-engineers alike, without condescension or jargon - Fluent in Spanish; working English for cross-team collaboration with our India and international colleagues MINDSET - Product-minded: you understand the business outcome behind the ticket you're working on - Comfortable moving between mobile and backend as neede