Telephony Engineer - Spain

About HappyRobot HappyRobot is the AI-native operating system for the real economy—a system that closes the circuit between intelligence and action. By combining real-time truth, specialized AI workers, and an orchestrating intelligence, we help enterprises run complex, mission-critical operations with true autonomy. Our AI OS compounds knowledge, optimizes at every level, and evolves over time. We're starting with supply chain and industrial-scale operations, where resilience, speed, and continuous improvement matter most—freeing humans to focus on strategy, creativity, and other high-value tasks. You can learn more about our vision in our Manifesto. HappyRobot has raised $62M to date, including our last $44M Series B in September 2025. Our investors include Y Combinator (YC), Andreessen Horowitz (a16z), and Base10—partners who believe in our mission to redefine how enterprises operate. We're channeling this investment into building a world-class team: people with relentless drive, sharp problem-solving skills, and the passion to push limits in a fast-paced, high-intensity environment. If this resonates, you belong at HappyRobot. About the Role We're looking for a Telephony Engineer based in Madrid to own and scale the real-time voice infrastructure that powers HappyRobot's AI workers across Europe. You'll be the go-to person for everything telephony on this side of the Atlantic—from SIP trunking and SBC configuration to CCaaS integrations and network troubleshooting. Our European client base is growing fast across large-scale logistics, telcos, and enterprise operations, and we need someone who can deploy, debug, and evolve our voice infrastructure with the same speed and ownership mindset that defines the rest of the team. You'll work closely with our US-based telephony lead and the Forward Deployed Engineering team embedded with customers. This is a high-agency role. You won't be handed runbooks—you'll write them. If something breaks, you fix it. If a customer needs a trunk stood up by tomorrow, you make it happen. If a process doesn't exist yet, you build it. Responsibilities Own and operate European SBC infrastructure (OpenSIPS/Kamailio). Configure, monitor, and troubleshoot SIP trunks for enterprise clients. Ensure high-availability voice delivery with sub-second failover. Integrate AI voice agents with CCaaS/UCaaS platforms such as Genesys Cloud, Five9, NICE CXone, RingCentral, Zoom, 8x8, and others. Handle OAuth flows, SIP header parsing, queue routing, and agent-availability checks. Diagnose call quality issues—latency, jitter, one-sided audio, codec negotiation failures—using Wireshark, tshark, mtr, and ffmpeg. Capture and analyze SIP call flows end-to-end. Optimize call flows, IVRs, routing logic, and contact center performance across client deployments. Support trunk provisioning and incident resolution with carriers and telephony vendors as needed. Maintain and improve telephony infrastructure in Kubernetes. Write automation scripts and tooling in Golang, JavaScript, or Python. Contribute to CI/CD pipelines and monitoring. Join technical calls with enterprise clients and their telephony partners. Translate complex SIP and networking issues into clear language for non-technical stakeholders. Create and maintain documentation on infrastructure, integrations, and procedures. Help evaluate and deploy next-generation real-time communication tools (LiveKit, WebRTC) as the voice stack evolves. Requirements Deep SIP/VoIP expertise. You can read a SIP call flow in your sleep. You understand INVITEs, REGISTERs, codecs (PCMU, PCMA, G722), SRTP, DTMF (RFC 2833), and one-sided audio debugging. OpenSIPS or Kamailio experience. Hands-on experience configuring, scaling, and troubleshooting SIP proxy servers is essential for this role. Strong networking fundamentals. TCP/UDP, DNS, TLS, NAT traversal, firewall rules, port management. Proficient with Wireshark/tshark, mtr, traceroute, and packet-level debugging. CCaaS/UCaaS/PBX knowledge. Hands-on experience integrating with platforms like Genesys Cloud, Five9, NICE CXone, RingCentral, 8x8, Zoom, or similar contact center solutions. DevOps competency. Comfortable with Kubernetes, Git, and CI/CD pipelines. You don't need to be a 10x developer, but you must be able to tread water with code and leverage AI tools effectively. Proficiency in at least one of: Golang, JavaScript/Node.js, or Python for scripting, automation, and tooling. Audio engineering basics. Understanding of audio codecs, transcoding, ffmpeg, and media handling in RTP streams. Experience with system integration via APIs, webhooks, and middleware platforms. Strong troubleshooting skills across networks, voice quality issues, and platform interoperability in enterprise environments with high availability and scalability needs. Excellent communication and documentation skills. Fluent English, written and spoken. Nice to Have Networking or SIP School certifications. Experience with telephony vendors and SBC platforms such as Ribbon, Oracle, or Oculeus. Familiarity with LiveKit or WebRTC-based real-time communication frameworks. Experience working with European telcos and carriers. Carrier-side provisioning experience (number porting, trunk setup, regulatory compliance). Certifications in Genesys, NICE, or equivalent telephony solutions. Exposure to contact center analytics and reporting tools. Why join us? Opportunity to work at a high-growth AI startup, backed by top investors. Fast Growth - Backed by a16z and YC, on track for eight figure ARR. Ownership & Autonomy - Take full ownership of projects and ship fast. Top-Tier Compensation - Competitive salary + equity in a high-growth startup. Work With the Best - Join a world-class team of engineers and builders Our Operating Principles Extreme Ownership We take full responsibility for our work, outcomes, and team success. No excuses, no blame-shifting — if something needs fixing, we own it and make it better. This means stepping up, even when it’s not “your job.” If a ball is dropped, we pick it up. If a customer is unhappy, we fix it. If a process is broken, we redesign it. We don’t wait for someone else to solve it — we lead with accountability and expect the same from those around us. Craftsmanship Putting care and intention into every task, striving for excellence, and taking deep ownership of the quality and outcome of your work. Craftsmanship means never settling for “just fine.” We sweat the details because details compound. Whether it’s a product feature, an internal doc, or a sales call — we treat it as a reflection of our standards. We aim to deliver jaw-dropping customer experiences by being curious, meticulous, and proud of what we build — even when nobody’s watching. We are “majos” Be friendly & have fun with your coworkers. Always be genuine & honest, but kind. “Majo” is our way of saying: be a good human. Be approachable, helpful, and warm. We’re building something ambitious, and it’s easier (and more fun) when we enjoy the ride together. We give feedback with kindness, challenge each other with respect, and celebrate wins together without ego. Urgency with Focus Create the highest impact in the shortest amount of time. Move fast, but in the right direction. We operate with speed because time is our most limited resource. But speed without focus is chaos. We prioritize ruthlessly, act decisively, and stay aligned. We aim for high leverage: the biggest results from the simplest, smartest actions. We’re running a high-speed marathon — not a sprint with no strategy. Talent Density and Meritocracy Hire only people who can raise the average; ‘exceptional performance is the passing grade.’ Ability trumps seniority. We believe the best teams are built on talent density — every hire should raise the bar. We reward contribution, not titles or tenure. We give ownership to those who earn it, and we all hold each other to a high standard. A-players want to work with other A-players — that’s how we win. First-Principles Thinking Strip a problem to physics-level facts, ignore industry dogma, rebuild the solution from scratch. We don’t copy-paste solutions. We go back to basics, ask why things are the way they are, and rebuild from the ground up if needed. This mindset pushes us to innovate, challenge stale assumptions, and move faster than incumbents. It’s how we build what others think is impossible.