Senior Backend Engineer – C#/.NET

Your mission Location: remote within Germany JTL is one of the leading providers of e-commerce software in the German-speaking region — with around 450 employees across the group and more than 50,000 customers across 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. You'll join the team behind our Fulfillment Network — the backend that keeps orders, stock, and logistics flowing for thousands of merchants. We care about systems that stay up and get better with every release, and we keep ownership close: the people who build a service also run it. You'll fit in here if you like backend problems that carry real operational weight. This is a backend-first role — you think of yourself primarily as a backend developer, and the core of the work lives in the .NET / MongoDB space. You'll develop the REST API behind our Fulfillment Network (FFN) and Trade Network (TDN), products used by thousands of customers every day, and own the integration points where backend services and the JTL-Wawi client need to work together seamlessly. You think in systems and data flows rather than isolated tickets, switch comfortably between technologies, and thrive in a fast-moving, startup-like environment. The principle here is simple: you build it, you run it. You don't own the underlying hardware, but you own your application's operational readiness end to end — when outages happen, you resolve them the same business day. Stability and availability matter to you as much as shipping new features, and you take pride in making the product faster and more reliable with every iteration. Your Responsibilities Develop our FFN / TDN REST API further and own backend features end to end, from design to productionBuild the integration with JTL-Wawi, especially where backend services and client-side behavior need to work together seamlesslySupport complex business and synchronization scenarios, and handle production incidents and customer-reported issuesOperate and deploy the API through our pipelines — covering performance optimization, observability, and operational reliabilityOwn the operational readiness of your application end to end: you build it, you run it, and you resolve outages within the same business day Your profile C#, modern .NET (.NET 8+), and ASP.NET Core are your primary stack — with solid, hands-on experience building and operating backend services in productionYou've built and maintained complex backend systems with a focus on robustness, maintainability, and scalability — using modern .NET patterns (async/await, dependency injection, clean architecture), CQRS, and Domain-Driven Design (DDD)You know MongoDB well (data modeling, performance optimization, high-volume datasets) and have strong SQL skills, including writing and optimizing complex queries for performanceYou design and consume REST APIs on both sides (Core & Connect), and you can identify and resolve bottlenecks across APIs, database access, and backend workflowsYou have hands-on observability experience with Prometheus and Grafana — metrics, dashboards, alerting, production analysis — and you resolve customer-reported issues pragmatically and reliablyYou've worked with AI-assisted development and agentic, automation-first engineering where it creates real valueYou have good German communication skills Nice to have ERP or e-commerce backgroundLogistics or fulfillment domain knowledgePHP — practical production experience, ideally within the Laravel ecosystemMariaDB / MySQL — data modeling and query optimizationLivewire / Tailwind — no deep expertise required, but able to work independentlyWPF — practical experience working on existing desktop UI applicationsDevExpress — experience with component-based desktop UI development Why us? Remote-first within Germany, with the option to work remotely from eligible countries for up to 180 days per yearMeal allowance of up to €115 net per monthErgonomic workspace allowance for your home office setupRegular team events, company-wide gatherings, and summer and Christmas parties to stay connected as a remote-first companyEGYM Wellpass and JobRad subsidyFinancial benefits including capital-forming payments (Vermögenswirksame Leistungen) and a 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!