Senior Software Engineer - Real-Time Voice and Audio Systems

This is a role that TechTree is recruiting for on behalf of one of our clients. TechTree is an AI-driven recruitment platform working with high-growth companies. When you apply, our AI Agent matches you not just to this role, but to other relevant opportunities across our network, so one application can unlock multiple roles. Senior Software Engineer — Build real-time voice and audio systems from zero for European defence customers. Paris or Warsaw, on-site. A European defence startup based between Paris and Warsaw is building modern software tailored for hostile environments. Customers include European military and police units. Recognised as one of France’s top 20 seed companies and backed by Europe’s leading defence VC and angels including the founders of Cloudflare, Quantum Systems, and ElevenLabs. Founding team: two early Cloudflare employees and a former GIGN commander. No weapons systems. No hardware. You’ll work closely with the founders to iterate quickly on deployments of prototypes with early customers. What You'll Do → Ship and iterate on prototype deployments directly with early customers → Get hands-on with bespoke audio streaming tech and real-time voice systems → Build from zero alongside the founding team What We're Looking For → Pragmatic, product-minded software engineering generalist with strong execution skills → Thrives in ambiguous, fast-moving environments → Can explain complex technical systems in simple ways → Speaks French and English Bonus → Worked with LLMs, or built pipelines → Comfortable with audio processing and low-latency systems → Experience in on-prem environments → Implemented AI systems in resource-constrained environments → Experience working with armed forces Location: Paris or Warsaw, on-site (relocation support available) Compensation: €85–105K + equity, depending on experience What is TechTree? TechTree combines AI agents with a human support team to give candidates a better, more transparent hiring experience. Our AI Agent gets to know your background, experience, and what you’re optimising for. It continuously matches you to live roles across our network where there’s genuine alignment, not just keyword overlap. Our Human Team is there to support you through the process — answering questions, adding context, and making sure you’re never left guessing or ghosted. We only post real jobs. Every role on TechTree is a live, active hire.