Full-Stack Engineer

This position is listed on behalf of a partner company, which manages all applications and next steps. Our partner is looking for a Full-Stack Engineer (Backend Leaning) – Payments Engineering based in Spain. As a Full-Stack Engineer specializing in backend development, you will help build and evolve the payment infrastructure that powers a rapidly growing AI technology platform. You will work on critical systems responsible for billing, usage tracking, pricing, and payment processing across self-service and enterprise customers. Your work will directly impact revenue accuracy, customer experience, and the reliability of financial operations. You will contribute to modernizing existing systems, developing scalable event-processing services, and integrating new payment solutions while ensuring seamless migrations. Working closely with Engineering, Product, Growth, Finance, Tax, and Sales teams, you will solve complex technical challenges in a fast-paced, AI-first environment. This remote opportunity offers significant technical ownership, opportunities to tackle challenging engineering problems, and the freedom to make a measurable impact on products used by millions of people and businesses worldwide. Accountabilities
* Design, develop, and maintain reliable payment and billing systems that support customer transactions, pricing models, and revenue operations across self-service and enterprise offerings.
* Build and improve usage-tracking and metering systems to ensure accurate measurement of customer activity while minimizing performance overhead and latency.
* Lead and contribute to the migration and modernization of enterprise pricing and usage-processing infrastructure, including the development of stream-processing services for usage events.
* Improve payment experiences by simplifying customer upgrades and transactions, supporting payments through different legal entities, and integrating additional payment providers.
* Collaborate with Finance and Tax teams to meet compliance, auditing, reporting, and financial accuracy requirements.
* Partner with Product and Growth teams to implement pricing changes, support experimentation, and enable new commercial strategies.
* Investigate and resolve complex billing issues by analyzing customer journeys, application logs, system behavior, and code to identify root causes and implement lasting solutions.
* Design and implement secure, scalable APIs, backend services, data storage solutions, and supporting infrastructure.
* Plan and execute migrations and system changes carefully, ensuring backward compatibility, minimizing disruption, and protecting customers from billing errors or payment interruptions.
* Work cross-functionally with engineers, Sales teams, Forward Deployed Engineers (FDEs), Finance specialists, and other stakeholders to deliver robust payment solutions.
* Maintain high standards for testing, security, code quality, observability, and operational reliability across systems that process financial transactions.
* Take ownership of technical challenges from investigation and design through implementation, deployment, monitoring, and continuous improvement. Requirements
* Strong Python expertise: Demonstrated proficiency in Python and the ability to build maintainable, reliable, and efficient software.
* Backend engineering

experience:
A strong background in backend development, including designing and operating production systems.
* Software and system design: Solid understanding of common software architecture and design patterns, APIs, cloud infrastructure, storage technologies, and data structures.
* Testing and security: Strong fundamentals in test design, automated testing, application security, and building dependable production systems.
* Production debugging: Ability to investigate complex technical issues, analyze logs and application behavior, identify root causes, and implement effective solutions.
* System adaptability: Ability to quickly understand a large existing codebase and navigate complex infrastructure, legacy components, and interconnected services.
* Financial accuracy and attention to detail: A careful, methodical approach to modifying live systems that handle payments, pricing, usage data, and revenue.
* Migration and reliability mindset: Ability to plan and execute system changes safely, manage technical risks, and minimize disruption to customers and business operations.
* Ownership and problem-solving: A proactive, independent approach to solving challenging engineering problems, making sound technical decisions, and delivering measurable results.
* Cross-functional collaboration: Strong communication skills and the ability to work effectively with engineering, product, growth, finance, tax, and commercial teams.
* Flexible

qualifications:
No formal degree, certification, or specific length of professional experience is required. Demonstrated ability to solve difficult technical problems through previous projects, open-s