Senior Backend Developer (Services)

Senior Python Backend Developer (Services)Payabl. empowers businesses to grow through payments innovation and banking services. Our ambition is to expand our strong portfolio of global financial services and make them all accessible through our unified platform, payabl.one. As a licensed financial company with principal membership with card schemes, we specialize in global payments and multi-currency banking solutions.The role is about: We are looking for a Senior Python Backend Developer (Services) to join our engineering team and contribute to the evolution of our service layer architecture.This role is focused on designing and building reliable, scalable microservices while also working with and gradually transforming legacy systems. You will play a key role in extracting business logic from existing codebases and reimplementing it into modern, maintainable Python services.This is a hands-on engineering role requiring strong problem-solving skills, attention to detail, and a deep understanding of backend systems reliability. Success in this role means going beyond "it works" — ensuring correctness, resilience, and long-term maintainability.Location: Remote from Portugal / Ukraine (Contractor arrangement) Reporting to: Engineering LeadWhat You'll DoDesign, build, and maintain high-performance Python microservices (FastAPI, AsyncIO)Analyze legacy systems and extract business logic into modern architecturesRefactor and migrate existing modules into clean, scalable, and maintainable servicesEnsure system reliability through idempotency, fault tolerance, and robust error handlingDesign and integrate external APIs, handling edge cases, retries, and failuresImplement and manage webhooks, callbacks, and complex retry mechanismsWrite high-quality unit and integration testsCollaborate with cross-functional teams to ensure service stability and performanceContribute to architectural discussions and continuous system improvementsTake ownership of services end-to-end, from design to productionWhat We're Looking For5+ years of backend development experience with strong Python expertiseDeep knowledge of AsyncIO and FastAPIExperience building non-blocking, high-reliability microservicesStrong experience with relational databases (MySQL, PostgreSQL)Solid understanding of API design and third-party integrationsExperience implementing webhooks, callbacks, and retry strategiesStrong testing practices (unit and integration testing)Ability to work with legacy systems and migrate them into modern architecturesStrong analytical and problem-solving skillsOwnership mindset and ability to work autonomously within a defined architectureNice to HaveExperience with PHP, Perl, or JavaScriptFamiliarity with Kafka, Redis, or event-driven architecturesExposure to CI/CD pipelines, Docker, and KubernetesExperience in fintech, payments, or e-commerce domainsKnowledge of 3DS, tokenization, or payment gateway integrationsProven experience migrating systems across technologies or paradigmsEngineering Culture & EnvironmentClear architectural direction with full ownership of implementationStrong emphasis on engineering quality, reliability, and accountabilityOpen to new tools, ideas, and technologies that bring measurable valueCollaborative environment with room to influence technical decisionsDedicated DevOps support, with opportunities to contribute if desiredWhat to ExpectA balanced role between building new services and modernizing legacy systemsComplex, real-world engineering challenges in a high-reliability environmentOpportunity to shape the evolution of a modern service-based architectureA team that values autonomy, ownership, and pragmatic problem-solvingHiring ProcessTA Interview (30–40 min): Experience, problem-solving, and cultural fitTechnical Interview (90 min): Combined system discussion and live coding sessionFinal Interview: Team and leadership alignmentWhy Join Payabl.?Work on high-impact systems in a fast-growing fintech environmentBe part of a team that values ownership, adaptability, and engineering excellenceHelp modernize and scale a platform handling real-world financial operationsContribute to meaningful technical decisions and system evolutionLet's embark on a journey to redefine the landscape of payments together. We're not just offering a role; we're inviting you to be a part of something bigger. Join our team, and let's innovate, disrupt, and lead the future of payments. Together, we can make an impact that resonates.