Role: Senior / Principal Software Engineer Job Type: Full-Time Salary range: to €100.000 + Equity Contract type: Direct employment with our client Location: Onsite in Barcelona Only interested in speaking with candidates who are comfortable working from the office 5 days per week Our partner is building next-generation AI-driven communication products that help businesses automate customer interactions, improve operational efficiency and generate actionable insights in real time. They are now looking for a Senior/ Principal Software Engineer to help scale the platform behind their voice agents, owning features end-to-end across their TypeScript / Python stack and working on AI pipelines, LLM orchestration, STT/TTS, prompt workflows and real-time systems. What we are looking for

+5-7 years of production experience with modern web stack Experience with AI coding agents such as Claude Code, Cursor or Codex Real Product mindset and ability to work autonomously Comfortable with Docker, SQL,



testing and scalable architecture Fluent Spanish and English Nice to have

Experience with LLMs, STT/TTS, OpenAI, Whisper, ElevenLabs or Deepgram Experience with LangChain, LangGraph or similar AI orchestration tools AWS/GCP, CI/CD and observability experience Startup or early-stage product company experience PRevious experince leading a team or acting as a principal What you’ll be doing

Building scalable APIs and services for real-time voice interactions Developing product features end-to-end with React, TypeScript and AI infrastructure Integrating LLM, STT and TTS workflows into production Working on agentic and multi-agent workflows Improving architecture, observability, testing and engineering quality Working directly with the founders and senior team to shape the platform

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📌 Senior Software Engineer (Madrid)
🏢 Concentric Recruitment
📍 Madrid