Senior Full Stack / Backend Engineer

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.