Senior VoIP Engineer Voice AI & New Product Development - English

Our client is a fast-growing technology organisation specialising in SaaS solutions for voice and SMS communications, supporting performance marketing and lead generation at scale. With a global customer base and high-volume, carrier-grade infrastructure, the company is focused on delivering reliable, scalable communication solutions in a fast-paced and highly regulated environment. The team is lean, international, and fully remote, with colleagues working across Europe.

Currently expanding, they are looking for a driven Senior VoIP Engineer Voice AI & New Product Development with a focus on taking new voice products and technologies from architecture to production.

Job Profile for Senior VoIP Engineer Voice AI & New Product Development
Responsibilities will include, but not be limited to:

• Design, develop, and maintain VoIP applications using Asterisk 22, OpenSIPS, and supporting technologies
• Build backend services and integrations using Java/Spring Boot
• Build and integrate production-ready voice AI agents with high audio quality and low latency
• Design and deliver new voice products, including ringless voicemail, branded calling, and advanced routing
• Implement SIP routing, call flows, dialplans, STIR/SHAKEN, media handling, and custom modules
• Develop REST/ARI services and automation for telephony workflows
• Troubleshoot and optimise SIP/RTP performance, including packet-level analysis
• Deploy and manage scalable VoIP infrastructure on GCP, including MIGs, networking, load balancing, and IaC
• Ensure SIP security, fraud prevention, resiliency, and high availability
• Collaborate with DevOps, networking, and QA teams

Candidate Profile for Senior VoIP Engineer Voice AI & New Product Development

• Must be fluent in English, both written and spoken
• 5+ years of hands-on VoIP engineering experience, ideally within a CPaaS, telco, or voice infrastructure company
• Strong Asterisk 22 experience, including dialplans, ARI/AMI, PJSIP, and audio codecs
• Solid OpenSIPS experience, including SIP routing, modules, registrar, dispatcher, and scripting
• Strong Java programming skills, ideally with Spring Boot or similar frameworks
• Strong networking knowledge across SIP, RTP, TCP/UDP, NAT traversal, QoS, DNS, TLS, firewalls, and packet analysis
• Hands-on experience with voice AI in production, including TTS, STT, and real-time conversational AI
• Strong GCP experience, including Compute Engine, VPC, load balancing, monitoring, Linux administration, and shell scripting
• Experience with STIR/SHAKEN implementation and ringless voicemail (RVM)
• Understanding of distributed systems, microservices, high-availability architecture, and scalable infrastructure
• Familiarity with the voice AI ecosystem, including ElevenLabs, Deepgram, OpenAI Realtime, Cartesia, and Vapi
• Strong ear for audio quality, with a focus on production-ready voice experiences
• Open-source contributions in voice, telephony, or audio AI
• Experience with Docker/Kubernetes, CI/CD, NoSQL/time-series databases, and message queues is a plus