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. ISO27001, 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, 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
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.
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