Senior Software Engineer (Backend-Leaning Full Stack)

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior Software Engineer (Backend-Leaning Full Stack) based in Germany. This role offers the opportunity to build and evolve commercially critical infrastructure for a growing payment technology platform. You will work primarily on backend systems while contributing across the full stack when needed, with an approximate 80/20 backend-to-frontend focus. Your work will span payment and billing integrations, data pipelines, reconciliation, orchestration, notifications, and customer-facing functionality. You will own projects end to end, from understanding business and technical problems through architecture, implementation, testing, and production delivery. The environment emphasizes autonomy, strong engineering judgment, and the ability to make sound decisions without highly prescriptive specifications. AI-assisted development is an important part of the engineering workflow, with an expectation that you can use modern tools while maintaining rigorous technical judgment. This is an ideal opportunity for a self-directed engineer who wants meaningful ownership, fast feedback, and a direct impact on a growing business. Accountabilities Own software projects end to end, from understanding business or technical objectives and designing solutions through implementation, testing, deployment, and production ownership.Design, build, and maintain reliable backend systems supporting payment recovery, billing, and subscription-related workflows.Develop and manage integrations with payment providers, third-party APIs, and other external services.Build robust data models, ingestion pipelines, reconciliation processes, and systems that support accurate and scalable data operations.Design and improve retry, orchestration, and payment recovery infrastructure with a strong focus on reliability and resilience.Contribute to machine-learning experiments, performance analysis, and data-driven initiatives that improve product and business outcomes.Develop and maintain email and push notification workflows, internal tools, and customer-facing product functionality.Contribute across the frontend when required, working with Next.js and React while maintaining a primarily backend-focused scope.Make architectural and technical decisions independently, particularly when requirements are incomplete or evolving.Identify potential failure modes, edge cases, scalability concerns, and operational risks before they affect production systems.Use AI-assisted development tools to accelerate implementation, prototyping, and problem-solving while carefully reviewing and validating generated code.Participate in code reviews, sprint planning, reviews, and collaborative engineering practices within a distributed team.Continuously improve engineering processes, technical solutions, and development practices as the product and business scale. Requirements 4+ years of professional software engineering experience.Strong backend engineering expertise combined with the ability to contribute effectively across the full stack.Professional experience with Python, Next.js, React, and PostgreSQL is highly relevant to the role.Proven ability to independently design, build, ship, and maintain production systems.Strong system design skills and sound technical judgment, with the ability to make effective decisions in ambiguous environments.Solid experience working with APIs, databases, third-party integrations, and production infrastructure.Experience with payment systems, fintech, billing, subscription infrastructure, or other transaction-heavy environments is a strong advantage.Experience building data ingestion, reconciliation, orchestration, or other reliability-critical systems is desirable.Experience working with multiple third-party services and integrations.Experience in an early-stage startup or small engineering team is beneficial.Demonstrated abil