Senior Full Stack / Backend Engineer — Voice & AI
VoiceB | Fully Remote (Spain) | Engineering
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We're VoiceB. We're building the autonomous AI voice sales agent that's automating the last undigitized sales channel: the phone call. Top enterprise brands across telco, banking, insurance, energy and automotive are already using our platform to handle inbound B2C and B2B sales conversations end-to-end — qualifying, pitching, and closing without human agents.
We're profitable, growing fast, and just getting started. Now we're hiring a Senior Engineer to help us scale the core platform that powers it all.
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🎯 What you'll do
• Design and build core systems behind our autonomous voice agent platform — real-time voice pipelines, LLM orchestration, telephony integrations and CRM connectors.
• Own the voice infrastructure layer: Twilio, SIP trunks, WebRTC, and the real-time audio plumbing that makes a sub-second AI conversation feel human.
• Ship full stack when needed — backend is your home, but you're comfortable touching the frontend to deliver end-to-end.
• Work directly with our CTO and a small, senior engineering team where every line of code matters.
• Integrate with Salesforce, HubSpot, ad platforms (Google, Meta) and enterprise CRMs.
• Contribute to architecture decisions that will define how voice AI scales over the next 5 years.
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✅ What we're looking for
• 5+ years building production backend systems (Node.js, Python, Go, or similar).
• Hands-on experience with Twilio and voice infrastructure — SIP, WebRTC, RTP, codecs, real-time audio. This is non-negotiable.
• Experience integrating and working with LLMs, STT/TTS pipelines, or AI/ML systems in production.
• Full stack capability — you can move across the stack when the product needs it.
• Strong systems thinking: latency, concurrency, reliability at scale.
• Advanced English (C1+). You'll work daily with enterprise customers and a global team.
• Hard worker, ownership mindset, comfortable in a high-velocity startup environment.
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🎁 Nice to have
• Experience with conversational AI, IVR systems, or contact center platforms.
• Background in CRM integrations (Salesforce, HubSpot).
• Previous exposure to enterprise-grade compliance (GDPR, ISO 27001, SOC 2).
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💼 What we offer
• Fully remote within Spain, with access to a coworking space if you want one.
• Reporting directly to Luis Miguel, our CTO.
• Market-rate salary + equity compensation after your first year.
• A small, senior team working with some of the largest brands in Europe.
• Real ownership over critical product areas — no layers, no politics.
• A category-defining product at a category-defining moment for AI.
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📍 Location: Spain (fully remote)
🗣️ Language: English (advanced+), Spanish a plus
👤 Reports to: CTO
If you want to build the infrastructure that's automating the world's last analog sales channel — and do it alongside a team that ships — let's talk.
Apply directly through LinkedIn.