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

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