Senior Fullstack Engineer

Your mission JTL is one of the leading providers of e-commerce software in the German-speaking market. With our Warehouse Management System (WMS), we support our customers in processing thousands of orders every day – from goods receipt and picking to shipping. Performance, stability, and reliability are therefore business-critical. Today, our WMS is closely integrated with our ERP system. Step by step, we are evolving the architecture by introducing clearly defined interfaces, modern APIs, and new cloud services. At the same time, we are modernizing a system that is already heavily used in production – without disrupting ongoing operations. This is a technical challenge with a direct impact on our customers. To support this journey, we are looking for a new team member to join our team of six developers and two QA Engineers. As a Fullstack Software Engineer, you will work across different technologies and application layers: from modern web applications built with React and TypeScript, to our desktop applications built with WPF, and backend services and APIs based on C# and .NET. We work in two-week sprints, make technical decisions collaboratively, and actively use modern AI tools such as Claude Code and GitHub Copilot in our daily development work. Your responsibilities You develop and evolve our WMS as a Fullstack Software Engineer across frontend, desktop, and backend applications You help shape the step-by-step modernization of the WMS monolith and contribute to sustainable technology and architecture decisions You develop modern web applications and user interfaces using React and TypeScript You develop and modernize desktop applications based on WPF You develop backend components, services, and APIs using C# and .NET You contribute to the gradual decoupling of the WMS from the ERP system and develop the interfaces through which both systems will communicate in the future Your profile Several years of experience as a Software Engineer with a strong Fullstack development background Very good knowledge of C# and the .NET ecosystem (.NET 10+) Strong experience developing modern web applications with React and TypeScript Solid experience in desktop application development with WPF Experience developing and integrating APIs, particularly REST and GraphQL Experience working with relational databases, particularly Microsoft SQL Server Experience modernizing mature software landscapes, for example through modularization, API-based integration, and incremental migration A strong focus on quality, automated testing, maintainability, and operating your own services (“You build it, you run it”) Experience with AI-assisted software development, or a willingness to actively use modern AI tools in your daily development work You are fluent in English and have a very good command of German, both written and spoken Why us? Remote-first within Germany, with the option to work remotely from eligible countries for up to 180 days per year Meal allowance of up to €115 net per month Support for setting up an ergonomic home office Regular team events, company-wide gatherings, and summer and Christmas celebrations EGYM Wellpass and JobRad subsidy Employee savings benefits and company pension scheme About us JTL is one of the leading providers of e-commerce software in the German-speaking region – with around 450 employees across the group and 50,000 customers from a wide range of industries. We develop scalable, flexible solutions for the online retail of the future – from ERP systems to shop and marketplace integrations. Fairness and respect are part of our everyday practice. Are you committed, curious, and eager to work in a team while taking on responsibility? Are you looking for a job where Monday isn’t the worst day of the week? Then we look forward to receiving your application!