Lead VOIP Engineer; FreeSWITCH & Kamailio

Lead VOIP Engineer (Free SWITCH & Kamailio) – Synthflow AI

Location: Berlin/Remote

Job Type: Full-Time

Experience Level: Senior

Synthflow AI is a no-code platform for deploying voice AI agents that automate phone calls across contact center operations and business process outsourcing (BPO)  help mid-market and enterprise companies manage routine calls to save teams time and resources.

Our agents have already delivered measurable impact:

• Over 5 million hours of contact center operations saved
• 35% more calls answered compared to non-AI operators
• 45 million calls handled with a 99.9% uptime

Backed by Accel, Atlantic Labs, and Singular, and trusted by over 1,000 customers, our growth leads an industry shift toward sophisticated and accessible conversational AI.

About the Role

We are seeking an experienced VOIP Engineer with strong background in Free SWITCH and Kamailio to join our team. The ideal candidate will have extensive experience in SIP-based communications, RTP streaming, and conferencing solutions, along with a deep understanding of high-load production environments. You will design, implement, and optimize scalable VOIP solutions while ensuring high availability and performance.

• Design, deploy, and maintain Free SWITCH and Kamailio-based VoIP solutions.
• Configure and troubleshoot SIP protocols, RTP streams, and media gateways.
• Monitor and optimize high-load production Free SWITCH and VOIP systems.
• Implement and manage SIP monitoring tools like Homer or other real-time debugging solutions.
• Develop and fine-tune call routing, failover mechanisms, and load balancing strategies.
• Ensure security, scalability, and redundancy in the VoIP infrastructure.
• Troubleshoot and resolve VoIP-related issues in production environments.
• Collaborate with development, Dev Ops, and support teams to improve system performance.
• Work with SIP Trunks, SBCs (Session Border Controllers), and Media Servers.
• Implement WebRTC-based voice and video solutions.
• Document system configurations, troubleshooting guides, and best practices.

• 5+ years of experience in VOIP engineering, particularly with Free SWITCH and Kamailio.
• Strong expertise in SIP protocol, RTP streaming, and VoIP call flows.
• Experience working in high-load production Free SWITCH environments.
• Hands-on experience with Homer SIP capture or similar SIP monitoring tools.
• Deep understanding of NAT traversal, STUN/TURN, WebRTC, and ICE frameworks.
• Strong knowledge of load balancing, failover strategies, and traffic optimization.
• Proficiency in Linux administration, networking, and troubleshooting.
• Experience with database integration (Redis, Postgre
  
  SQL, or No
  
  SQL solutions).
• Familiarity with WebRTC, Asterisk, OpenSIPS, or RTP Proxy is a plus.
• Ability to write Bash/Python (or Golang) scripts for automation and monitoring.
• Strong problem-solving skills and ability to work in highly available and scalable environments.

Founded in Berlin in 2023 by serial entrepreneurs Albert Astabatsyan, Hakob Astabatsyan, and Sassun Mirzakhan-Saky, Synthflow AI democratizes access to advanced voice AI with a no-code platform that lets enterprises easily create, deploy and scale natural-sounding, cost-effective voice agents tailored to their business needs.