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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Senior Backend Software Engineer - **Company:** Fourthline - **Location:** Madrid, Spain - **Contract:** Permanent contract - **Skills:** .NET Framework, Amazon Web Services, Unit Testing, Microsoft Azure, C Sharp (Programming Language), Software as a Service, Continuous Integration, Relational Databases, Software Design Patterns, Language Integrated Query, Electronic Signatures, PostgreSQL, Nunit, Queueing Systems, RabbitMQ, Mstest, Software Engineering, .NET Core, Backend, Git, Xunit, Solid Principles, Restful APIs, Terraform, Domain Driven Design, Docker, Web Api, Programming Languages, Microservices - **Published:** August 5, 2026 - **Apply:** https://www.buscojobs.com.es/senior-backend-software-engineer-en-madrid-ID-365561784 ## About the Role Minimum 5 years software development experience in one or more general-purpose programming languages. Good knowledge of . NET 5-8, or . NET Core 3.x Proficiency in C# (version 10 or later). Experience in unit and integration testing with XUnit (MSTest/NUnit are a plus). Familiarity with ORMs (EF Core) and knowledge of Linq. Experience implementing REST APIs using . NET Web API. Understanding of SOLID principles and Domain-Driven Design (DDD). Knowledge of common software design patterns. Experience with Git and CI/CD in Azure DevOps. Experience with cloud providers such as AWS and Azure; experience with EKS and Terraform is highly valued. Ability to work on-site at our fantastic office in Barcelona at least 3 days a week as per our Hybrid Working Policy. Language skills: English full professional proficiency. ## Description At Fourthline, our mission is to fight financial crime.We help protect the global financial system by verifying millions of identities for banks, neobanks, online brokers, crypto exchanges, and insurers like N26, Trade Republic, flatexDEGIRO, Nationale Nederlanden, Qonto, Shine, Solarisbank, and more.Having started our journey in January ****, we're incredibly proud to count around 250 employees between our Amsterdam and Barcelona offices with over 50 nationalities.Prevent financial crime by building best-in-class SaaS solutions with our talentedAnti-Money Laundering (AML) and Bank Account Verification (BAV) + Qualified Electronic Signatures (QES) teams in Barcelona -we're looking for a Senior Backend Software Engineer who brings solid technical expertise, a product-driven mindset, and a collaborative spirit across diverse domains and skill levels.As a Senior Backend Engineer At Fourthline, You WillDesign, develop, maintain, and improve our microservices, and take responsibility for thorough testing and reliable deployments of your stories.Professionally manage your tasks, priorities and deliverables, taking joint ownership with your teammates for the sprint goals.Utilize your experience to contribute to our growth through lessons learned from your successes and failures.Take responsibility for engineering excellence and participate in architectural decision-making within your team.Contribute to thorough documentation-crucial for ensuring success and minimizing questions!Understand the entire development lifecycle and work closely with other members in squads, including Platform and QA teams.Employ both technical and soft skills to address challenges, recognizing that solutions often require a blend of technology-based and people-based strategies.Emphasis on CollaborationAt Fourthline, we foster a collaborative culture informed by industry knowledge (FinTech) and deep understanding of our business objectives.You will actively participate in chapter meetings, knowledge sharing sessions and cross-discipline alignments with other teams and engineering disciplines.Career Growth and DevelopmentAt Fourthline, we offer opportunities for learning and development, allowing you to work alongside and learn from experienced engineers.As you grow within our team, there are possibilities to grow to Staff Engineer level and beyond, with clear pathways to further your technical, problem solving and communication competencies, as well as build your knowledge of the FinTech industry.Our StackNET 5-8 - Our cloud-based microservices architecture includes REST APIs, Docker, Message Queues (RabbitMQ), RDBMS (PostgreSQL), Wolverine, Marten (Doc + Event stores), and much more!Job RequirementsMinimum 5 years software development experience in one or more general-purpose programming languages.Good knowledge of .NET 5-8, or .NET Core 3.xProficiency in C# (version 10 or later).Experience in unit and integration testing with XUnit (MSTest/NUnit are a plus).Familiarity with ORMs (EF Core) and knowledge of Linq.Experience implementing REST APIs using .NET Web API.Understanding of SOLID principles and Domain-Driven Design (DDD).Knowledge of common software design patterns.Experience with Git and CI/CD in Azure DevOps.Experience with cloud providers such as AWS and Azure; experience with EKS and Terraform is highly valued.Ability to work on-site at our fantastic office in Barcelona at least 3 days a week as per our Hybrid Working Policy.Language skills: English full professional proficiency.At Fourthline, we believe diversity enriches our culture and inspires you to do your best work.We value your unique talents and perspectives, welcoming them into a safe and inclusive working environment, to ultimately deliver the best products to our customers and society.You're welcome here.Fourthline is for everyone.Our hiring process is designed to be equal, fair, and transparent.We welcome people from all backgrounds, ethnicities, genders, sexual orientations, ages, abilities, religions, and experiences in life.If you're excited about this role, but your experience does not align perfectly with every qualification in the job description, we encourage you to apply anyways.You may just be the right candidate for this or other roles.#J-*****-Ljbffr ## Related Videos - [Meet Your New BFF: Backend to Frontend without the Duct Tape](https://www.wearedevelopers.com/videos/682-meet-your-new-bff-backend-to-frontend-without-the-duct-tape) - [pytest: Simple, rapid and fun testing with Python](https://www.wearedevelopers.com/videos/213-pytest-simple-rapid-and-fun-testing-with-python) - [How a Small Team Shrank a Microsoft Monorepo by 94%](https://www.wearedevelopers.com/videos/1236-how-a-small-team-shrank-a-microsoft-monorepo-by-94) - [Using code generation for test automation – the fancy way](https://www.wearedevelopers.com/videos/230-using-code-generation-for-test-automation-the-fancy-way) - [Git for Code Reviews](https://www.wearedevelopers.com/videos/429-git-for-code-reviews) - [Back(end) to the Future: Embracing the continuous Evolution of Infrastructure and Code](https://www.wearedevelopers.com/videos/440-back-end-to-the-future-embracing-the-continuous-evolution-of-infrastructure-and-code) ## Related Articles - [Fully Remote Software Engineer Jobs](https://www.wearedevelopers.com/magazine/447-fully-remote-software-engineer-jobs) - [Software Engineer Salary London](https://www.wearedevelopers.com/magazine/252-software-engineer-salary-london) - [Frontend Developer Salary in The UK](https://www.wearedevelopers.com/magazine/233-frontend-developer-salary-in-the-uk) - [The Most Popular IT Jobs on the Market](https://www.wearedevelopers.com/magazine/376-the-most-popular-it-jobs-on-the-market) - [Top-Paying Tech Jobs (with Salaries)](https://www.wearedevelopers.com/magazine/372-top-paying-tech-jobs-with-salaries) - [The 12 Best Jobs for Software Engineers](https://www.wearedevelopers.com/magazine/401-the-12-best-jobs-for-software-engineers)