Senior Software Developer

Senior Software Developer (Voice / SIP Platforms) £55,000 £ 65,000 DOE | Hybrid Working (1x day a month office) Are you a seasoned developer with a passion for building robust, real-time communications platforms? Looking for a role where you can work on complex, enterprise-grade systems while still being close to the technical detail? This is an opportunity to join a well-established technology business with a strong reputation in communications and cloud-based solutions.

Youll be part of a small, highly skilled development team working on the evolution of a large-scale SIP platform and its associated APIs, with plenty of scope to influence design, tooling, and future direction.

The Role Working closely with the Development Manager, youll play a key role in enhancing and extending an existing SIP and VoIP platform used in production environments. This is a hands-on role suited to an experienced developer who enjoys solving complex protocol-level problems, building secure services, and integrating with third-party systems. Youll contribute across the full software lifecycle from design and development through to troubleshooting live issues while helping to improve development standards, security practices, and platform resilience.

Key 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. ISO
27001, PCI-DSS) Collaborate closely with other engineers and stakeholders, sharing knowledge and best practice Essential Skills & Experience Strong, hands-on experience with SIP/VoIP technologies and protocols (e.g. SIP, SDP, RTP, RFC
2833/4733) 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, SQL Alchemy, 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 Free SWITCH (configuration and/or source code exposure) Working knowledge of C or C++

Experience with Kamailio Authentication and authorisation frameworks (OAuth2, Auth0) Databases such as Mongo

DB and MySQL CI/CD pipelines (e.g. Git Hub Actions) Kubernetes, ArgoCD, or similar deployment tooling WebRTC experience Whats on Offer Salary up to £65,000 depending on experience Hybrid working model 24 days annual leave plus bank holidays Pension and life assurance Private medical insurance Birthday day off and paid volunteering day Cycle to Work scheme Retail and lifestyle discount programmes Interested?

If youre an experienced developer looking to work on technically challenging, real-time systems in a supportive and forward-thinking environment, wed love to hear from you. Apply now to learn more.