Software Engineer

Backend Developer (.NET 10) – Contract Location: Ivry-sur-Seine, France (Hybrid/Onsite as required) Start Date: ASAP Contract: Initial contract with potential extension Rate: Competitive (DOE) We're looking for an experienced Backend Developer (.NET 10) to join a high-performing Agile team delivering enhancements to a large-scale unified payments platform. This is an excellent opportunity to work on modern payment technologies, high-volume transaction processing, and cloud-native applications. Key Responsibilities Develop and enhance backend services for a unified payment platform using .NET 10.Design, build and maintain secure, scalable REST APIs.Deliver functionality across payment method eligibility, payment partner integrations and transaction management.Work on payment flows including card payments, digital wallets, authorisation, capture, refunds and 3D Secure.Improve application resilience, performance and overall platform quality.Produce unit tests and maintain high code quality standards.Document APIs and contribute to software craftsmanship best practices.Participate in Agile ceremonies including sprint planning, daily stand-ups, retrospectives and demos.Share knowledge around engineering best practices and AI-assisted development.Required Skills & Experience Expert-level experience with C# .NET 10 and ASP.NET Web API.Strong experience with MS SQL, Dapper and Microsoft Dependency Injection.Experience with xUnit, Moq and Postman.In-depth knowledge of payment systems and transaction flows, including CIT, MIT, 3DS, retries and idempotency.Experience with messaging technologies such as Kafka.Strong understanding of CI/CD, GitLab and cloud platforms, particularly Azure and Azure Container Apps (ACA).Experience with observability tools such as Datadog.Solid understanding of Clean Code, SOLID principles and software craftsmanship.Desirable Skills Visual Studio / Visual Studio Code.SQL Server Management Studio.Liquibase.WireMock.Experience working with GCP or other cloud platforms.What We're Looking For Excellent communication and collaboration skills.Self-motivated, proactive and able to work independently.Comfortable with pair programming and collaborative development.Passion for delivering high-quality, scalable software in an Agile environment