Software Engineer III – VoIP / FreeSWITCH

We're looking for an experienced FreeSWITCH Developer / VoIP Software Engineer to design, develop, and maintain the telephony solutions that power Vonage's call processing platform. You'll build real-time voice communication systems that handle millions of calls, developing features like call processing, recording, voicemail, conferencing, and external service integrations. This is a critical role where your work directly impacts business communications for customers worldwide.

What You'll Do

Core Responsibilities

• Build scalable telephony systems — Design and develop distributed, high-volume production telephony applications for our UCaaS platform that handle real-time voice traffic at scale
• Develop custom FreeSWITCH solutions — Create custom modules, dialplan configurations, and ESL (Event Socket Library) integrations for advanced call control and automation
• Deliver advanced telephony features — Implement call recording, voicemail transcription, fax processing, audio streaming, and other mission-critical voice features
• Rapid prototyping to production — Build proof-of-concepts quickly and evolve them into production-ready, maintainable code
• Drive technical innovation — Evaluate emerging telephony technologies and recommend architectural improvements that enhance our platform capabilities
• Mentor and lead — Guide team members on design patterns, best practices, and telephony architecture decisions

Day-to-Day Collaboration

• Participate in the full agile development lifecycle: sprint planning, design reviews, standups, and demos
• Respond promptly to production incidents affecting customers and business operations
• Work independently on end-to-end feature delivery while contributing to broader team goals
• Partner closely with Product Management, QA, and Operations teams to deliver cohesive solutions
• Communicate progress, blockers, and technical decisions clearly with engineering leadership

What You'll Bring

Required Experience & Skills

Telephony & VoIP Expertise (Must-Have)

• 6+ years of software development experience
• 3+ years hands-on experience with telephony platforms: FreeSWITCH, Asterisk, or similar open-source PBX systems
• Deep understanding of:
• SIP (Session Initiation Protocol) and RTP protocols
• VoIP architecture and NAT traversal techniques (STUN, ICE, TURN)
• Audio codecs (G.711, Opus, etc.)
• Dialplan development and call flow design

Programming & Development

• Strong proficiency in Java, C/C++, Python, and SQL
• Experience with CI/CD pipelines and modern development workflows
• Infrastructure as Code practices
• Containerization with Docker and Kubernetes

Cloud & Infrastructure

• Hands-on experience with AWS services: EC2, EKS, Lambda, S3, SNS, SQS, CloudFront
• Linux systems expertise: performance tuning, networking, file systems
• Database experience with:
• Relational: MySQL, PostgreSQL
• NoSQL: Redis, MongoDB

Problem-Solving & Debugging

• Proven troubleshooting skills in complex, distributed production environments
• Systematic debugging approach for real-time communication systems
• Experience analyzing performance bottlenecks and system failures

Nice to Have

• Experience with WebRTC
• Familiarity with Kamailio, OpenSIPS, or other SIP proxies
• Knowledge of PSTN interconnection and carrier integrations
• Previous UCaaS or CPaaS platform experience
• Contributions to open-source telephony projects
• Experience with monitoring and observability tools (Prometheus, Grafana, Datadog)

Why This Role Matters

As a FreeSWITCH Developer at Vonage, you'll work on voice infrastructure that powers critical business communications globally. Your code will directly enable features that millions of users depend on daily, and you'll have the opportunity to shape the architecture of next-generation voice platforms.

Work Style

• Ownership mindset — Take features from concept to production
• Collaborative approach — Work across teams while driving your work independently
• Customer focus — Balance feature velocity with reliability and user experience
• Continuous improvement — Stay current with telephony trends and share knowledge with the team