Staff Engineer — Real-Time Voice AI & Speech-to-Speech

Staff / Principal Engineer — Real-Time Voice AI & Speech-to-Speech21X | Detroit / Remote | Full-TimeWe’re Building the Best AI Voice Platform on the Planet. Come Own It.21X (formerly Structurely) isn’t another AI startup wrapping APIs around an LLM.We’ve spent 10+ years building conversational AI, powered over 500 million conversations, and earned the trust of some of the biggest names in financial services. Now we’re expanding aggressively into sports, private aviation, hospitality, and beyond. We have enterprise customers, proven technology, significant financial backing, and enormous ambition. Our voice platform already delivers exceptional speech-to-text, text-to-speech, and AI orchestration capabilities. But the next frontier is real-time speech-to-speech AI. And we intend to lead it. We’re looking for an exceptional Staff / Principal Engineer to help architect, build, and OWN the next generation of 21X Voice. This isn’t a maintenance role. It’s an opportunity to take an established enterprise AI platform and help make it the most natural, responsive, and intelligent voice experience in the world. You’ll work directly with our CTO and leadership team, make foundational architectural decisions, write production code, and help build the engineering team around this technology. We want a builder. An owner. Someone obsessed with winning. What You’ll OwnSpeech-to-Speech AI: Architect native, real-time S2S systems that move beyond traditional STT → LLM → TTS pipelines. Endpointing & Turn Detection: Build intelligent semantic endpointing, VAD, and conversational turn-taking systems. Natural Conversations: Engineer barge-in, interruption handling, full-duplex audio, and humanlike conversational flow. Ultra-Low Latency: Optimize streaming audio, inference, response timing, and time-to-first-audio. Voice Infrastructure: Build scalable real-time systems across WebRTC, WebSockets, SIP, RTP, and telephony networks. Agent Intelligence: Integrate real-time voice models with tools, enterprise workflows, and AI orchestration. Technical Leadership: Own architecture, influence the roadmap, mentor engineers, and ship production systems. What You MUST Bring 8+ years of software engineering experience building complex production systems. Hands-on experience building real-time speech-to-speech voice agents. Deep experience with endpointing, VAD, semantic turn detection, and interruption handling. Strong expertise in streaming audio, real-time inference, and latency optimization. Experience with WebRTC, WebSockets, RTP, or similar real-time protocols. Strong backend engineering skills in Python, TypeScript/Node.js, Go, or Rust. Experience building scalable distributed systems. A track record of taking technical ownership and shipping.