Senior Ultra-Low-Latency Network Engineer (Remote Spain) - Remote

Cactus is a software development company, providing full-cycle services for the European market. More than 170 companies increased business productivity using solutions developed by Cactus experts. The company has been regularly included in the listings of the best software development companies in Belgium and Europe. This position is based in Spain, and you will collaborate with teams across Europe and an international partnership landscape. What You Will Do Design and implement high-performance packet I / O pipelines using DPDK or equivalent frameworks. Adapt existing UDP application code to work with NIC queue–driven RX / TX loops, batch processing, and hardware offloads. Configure and tune Linux servers for ultra-low latency : hugepages, NUMA awareness, CPU pinning, NIC driver binding, RSS / flow steering. Ensure reliable operation at very high packet rates; instrument detailed throughput, latency, and packet-loss metrics. Collaborate with the application team to integrate kernel-bypass transport with existing processing pipelines. Stay current with RDMA and user-space networking trends (DPDK, netmap, AF_XDP, eBPF / XDP) to evaluate trade-offs. What We Expect Expert C / C++ in performance-critical networking code. Hands-on experience with DPDK or similar (AF_XDP, netmap, PF_RING) in production systems. Strong knowledge of Linux performance tuning and NIC hardware features (RSS, flow steering, checksum / jumbo offloads). Familiarity with RDMA (RoCE, InfiniBand, iWARP) concepts and when to use them vs. raw packet I / O. Experience with packet capture / analysis tools (tcpdump, Wireshark, perf). Strong problem-solving and debugging skills at the network + OS boundary. Excellent English communication skills – written and spoken.

• Preferred industry backgrounds : High-frequency trading (HFT) / fintech — ultra-low-latency networking engineers. Telecom / 5G / packet core — engineers building EPC, UPF, or fronthaul solutions. Network security & DPI appliances — intrusion detection / firewall data plane developers. CDN / video streaming / media transport — high-performance transport engineers. HPC / storage networking — experience with RDMA, NVMe-oF, or cluster interconnects. What We Offer Working with international clients. An environment to develop your professional capabilities and take ownership. Collaboration with a team of open, dynamic, and international experts. Full-time position with a competitive salary and benefits, including learning opportunities. Flexible working hours. Get-together team events.