Salary: £65,000 - 65,000 per year Requirements: Strong, hands-on experience with SIP/VoIP technologies and protocols (e.g. SIP, SDP, RTP, RFC2833/4733) 5 years experience developing in Python or another object-oriented language Solid understanding of object-oriented design principles Experience building and consuming HTTP/REST APIs Familiarity with Python frameworks and tooling such as Flask or Django, Pytest, SQLAlchemy, Marshmallow Strong background in secure systems design (software and network level) Proven experience using Wireshark for SIP/RTP analysis and fault-finding Version control experience with Git-based platforms Containerisation using Docker Strong Linux experience (Ubuntu-based systems) Excellent communication skills, comfortable working with both technical and non-technical stakeholders Desirable / Nice to Have: Experience with FreeSWITCH (configuration and/or source code exposure) Working knowledge of C or C++ Experience with Kamailio Authentication and authorisation frameworks (OAuth2, Auth0) Databases such as MongoDB and MySQL CI/CD pipelines (e.g. GitHub Actions) Kubernetes, ArgoCD, or similar deployment tooling WebRTC experience Responsibilities: Design, develop, and enhance a production SIP/VoIP platform and supporting services Build additional value-added services and integrations around the core platform Develop integrations with external systems, including AI-driven services such as speech recognition, transcription, and analytics Ensure secure design and implementation across software and infrastructure Diagnose and resolve complex SIP, RTP, and platform-level issues Contribute to secure development processes and compliance with recognised security standards (e.g. ISO27001, PCI-DSS) Collaborate closely with other engineers and stakeholders, sharing knowledge and best practice Technologies: AI ArgoCD CI/CD Cloud Django Docker Flask Git GitHub HTTP Kubernetes Linux MongoDB MySQL Network Python REST Security Ubuntu pytest More: We are a well-established technology business with a strong reputation in communications and cloud-based solutions, offering a hybrid working model that includes one day a month in the office. Our team comprises highly skilled developers focused on the evolution of a large-scale SIP platform and its APIs. We provide a competitive salary of up to £65,000 depending on experience, alongside benefits such as 24 days of annual leave plus bank holidays, a pension plan, private medical insurance, a birthday day off, and opportunities for paid volunteering. If you are an experienced developer seeking to work on technically challenging, real-time systems in a supportive and forward-thinking environment, we would love to hear from you. last updated 5 week of 2026