Staff Software Engineer (f/m/d) Software-Defined Networking

About IONOS At IONOS, we don't just manage servers – we shape the digital future for more than 6.2 million customers worldwide with our solutions. As Europe's leading hosting provider and a pioneer in independent cloud solutions, we are building next-generation infrastructure – from sovereign cloud architectures and high-performance GPU clusters to integrated AI automation tools. What drives us is digital sovereignty for Europe and real impact for small and medium-sized businesses (SMBs) as well as large enterprises. We work in agile teams, rely on transparent structures, and believe that excellence and innovation only emerge through true team spirit. Ready for your next step? Become part of IONOS and grow with us. The IONOS Cloud SDN Development team is seeking a highly motivated and experienced software engineer. The SDN Development team designs, develops and maintains the high-performance Software-Defined Networking (SDN) stack of IONOS Cloud: the networking foundation that connects our customers' virtual machines and cloud services. Our work spans the Linux kernel networking layer, virtual switching and the control plane. We use a range of technologies, from C/C++ and Golang for performance-critical components to Python for tooling and automation. Tasks Developing and supporting the scalable, high-performance SDN stack of IONOS Cloud using a range of diverse technologies. Designing new features and adopting new technologies (both hardware and "software defined") on different components of the SDN infrastructure. Writing and debugging C/C++ and Golang/Python code across the SDN data plane and control plane, from Linux kernel networking and eBPF to Open vSwitch/OpenFlow pipelines. Building Python tooling and automation for testing, deploying and operating the SDN stack, and troubleshooting network issues in virtualized environments (QEMU/KVM, VirtIO). Cooperating with other teams to ensure the smooth integration of new SDN features with different IONOS products. Qualifications Proficiency in C/C++ and/or Golang, plus Python, including AI-assisted development. Experience with Linux kernel networking internals. Knowledge of the TCP/IP protocol family and routing protocols like BGP, plus networking technologies such as Open vSwitch, OpenFlow, VXLAN, VRF and eBPF. Experience with cloud environments, Kubernetes and virtualization technologies like QEMU/KVM and VirtIO. Experience with the GNU toolchain (gcc, gdb, make, etc.), git and the Linux CLI. Experience with Linux system administration and automation. Nice to have: experience with VPP and DPDK. Benefits Hybrid working model. Flexible working hours through trust-based working hours. At some locations a subsidized canteen and various free drinks. Modern office space with very good transport connections. Various employee discounts for activities and products. Employee events such as summer and winter parties, as well as workshops. Numerous training and development opportunities. Various health offers, such as sports and health courses. Application Note We value diversity and welcome all applications – regardless of, for example, gender, nationality, ethnic or social origin, religion, disability, age as well as sexual orientation and identity, physical characteristics, marital status or any other irrelevant factor subject to applicable law.