Software Engineer III – VoIP / FreeSWITCH

Overview

Design, develop and maintain the telephony solutions that power Vonage's call processing platform, building real-time voice communication systems that handle millions of calls.

What you'll do

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

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

Details

• Location: Bangalore, India.