Backend Engineer (Billing)

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Backend Engineer (Billing) based in Spain. Join a fast-growing fintech engineering team building a new-generation billing platform from the ground up. You will work on a core product module responsible for invoicing, payment retries, subscriptions, and monetization. The role gives you ownership over foundational billing infrastructure, public APIs, pricing engines, and revenue recovery systems. You will help design scalable solutions for complex B2B pricing and high-volume payment workflows. Working primarily in Go, you will collaborate with experienced engineers and cross-functional specialists in a newly established Billing Stream. There is minimal legacy to maintain, giving you the opportunity to make meaningful architectural decisions from the start. This is a high-impact environment where strong engineering practices, automated testing, reliability, and continuous delivery are central to how products are built. Accountabilities Design and ship the foundational Products & Prices domain model and public APIs from the ground up.Build high-precision volume and graduated pricing engines capable of supporting complex, multi-tier enterprise billing requirements.Design and implement resilient billing services that minimize dependencies and eliminate critical single points of failure.Lead the automated payment retry engine across invoices to improve revenue recovery and reduce failed-payment impact.Develop reliable, scalable backend services capable of operating in high-load environments.Contribute to the evolution of the Billing 2.0 platform and help establish its architecture, standards, and engineering practices.Write and maintain comprehensive automated tests across unit, integration, functional, and end-to-end levels.Participate in code reviews, technical discussions, metrics and alerting practices, and continuous improvement of system reliability.Collaborate closely with product management, engineering, QA, and domain specialists to deliver billing capabilities end to end.Help build a modern, maintainable billing infrastructure with a strong focus on performance, reliability, and operational excellence. Requirements 2+ years of backend engineering experience using Go, PHP, Kotlin, Java, Python, Node.js, or a comparable backend technology.Strong willingness to work with Go; both experienced Go engineers and strong engineers transitioning from another backend language are encouraged to apply.Demonstrated experience writing and maintaining automated tests, including unit, integration, functional, and end-to-end tests.Strong understanding of high-load system design principles and scalable backend architecture.Experience working with PostgreSQL and queues or streaming technologies.Proactive, communicative, independent, and results-oriented approach to engineering.Ability to take ownership of technical problems, make sound decisions, and drive solutions forward.Experience with payment systems or previous work in fintech or financial services is a plus.Familiarity with Kafka, AWS services, and CI/CD pipelines is advantageous.Comfortable working in a collaborative engineering environment with code reviews, automated testing, observability, metrics, alerts, and continuous delivery. Benefits High-impact role with the opportunity to build a new billing platform and make meaningful architectural decisions rather than inheriting a mature legacy system.Opportunity to work on financial infrastructure supporting modern internet businesses across subscriptions, payments, chargebacks, fraud prevention, and indirect tax.Collaboration with a proven, results-driven engineering team in a rapidly scaling fintech environment.Modern engineering culture focused on technical discussions, code reviews, strong testing practices, metrics, alerts, and fully automated CI/CD.Significant career growth opportunities within a rapidl