Senior Software Developer

Senior / Experienced Software Developer

Location:

Guildford (Hybrid must be UK-based and within a two-hour commute)

Contract:

Full-time, Permanent Salary: £55,000 £ 65,000 (depending on experience) The Opportunity An established UK technology company is expanding its Software Development Team and is looking for an experienced Senior Software Developer to help evolve a large-scale, enterprise-grade SIP platform and its associated REST APIs. This is an excellent opportunity to work on complex, real-world systems in a collaborative, technically strong environment.

Youll contribute to the ongoing development of a mission-critical communications platform, build value-added services, and work with modern AI-driven integrations. The organisation is known for its strong engineering culture, long-term customer partnerships, and commitment to professional development. Youll be joining a supportive, innovation-led environment where your ideas and expertise will have a real impact. Role Summary Designing, developing, and enhancing an existing enterprise SIP platform and supporting services Building new value-added services and capabilities around the core platform Developing integrations with third-party systems, including AI-based voice recognition, transcription, and sentiment analysis services Ensuring secure software design and development at both application and network levels Analysing, troubleshooting, and resolving SIP/RTP and platform-level issues Contributing to secure development processes, policies, and compliance with standards such as ISO 27001 and PCI-DSS Collaborating closely with other developers and stakeholders to deliver high-quality, scalable solutions Essential Skills & Experience SIP / VoIP and related protocols (SDP, RTP, RFC
2833 / RFC
4733, etc.) Python or another object-oriented language (5 years) Object-oriented design principles HTTP / RESTful APIs Flask or Django, including Jinja, Pytest, SQL Alchemy, and Marshmallow Secure systems design and development (software and network level) SIP/RTP troubleshooting using tools such as Wireshark Git / Git Hub (or similar version control systems) Docker containerisation Linux (Ubuntu-based) environments A full driving licence and car due to the clients location Desirable Skills Free SWITCH (configuration and, ideally, source code) C / C++ (for open-source troubleshooting or minor code changes) Kamailio Auth0 / OAuth 2.0 Mongo

DB and/or MySQL CI/CD pipelines (e.g. Git Hub Actions) Kubernetes / ArgoCD WebRTC Benefits 24 days annual leave plus bank holidays Pension scheme Life insurance Private medical insurance Birthday and volunteering day off High street discount vouchers Thank you for taking the time to apply to OPR Resourcing Specialists. If your application is successful you will be contacted within 7 days.

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