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. You’ll 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. You’ll 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, RFC2833 / RFC4733, etc.)
- Python or another object-oriented language (5+ years)
- Object-oriented design principles
- HTTP / RESTful APIs
- Flask or Django, including Jinja, Pytest, SQLAlchemy, and Marshmallow
- Secure systems design and development (software and network level)
- SIP/RTP troubleshooting using tools such as Wireshark
- Git / GitHub (or similar version control systems)
- Docker containerisation
- Linux (Ubuntu-based) environments
- Full drviing licence with car due to the client's location
Desirable Skills
- FreeSWITCH (configuration and, ideally, source code)
- C / C++ (for open-source troubleshooting or minor code changes)
- Kamailio
- Auth0 / OAuth 2.0
- MongoDB and/or MySQL
- CI/CD pipelines (e.g. GitHub Actions)
- Kubernetes / ArgoCD
- WebRTC
Benefits
- 24 days’ annual leave plus bank holidays
- Pension, 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. We apologise but due to the high volume of applications we receive we are unable to provide feedback on individual CV's.
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If you do not currently have the Right to Work in the UK or will need additional support to extend your current Right to Work status, your application cannot be considered.
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