Lead VOIP Engineer (FreeSWITCH & Kamailio)

Synthflow AI is an enterprise AI agent platform that unifies customer operations across voice, chat, and messaging. Our agents handle routine interactions at scale so teams can focus on high-value work. Over 20M hours of operations automated 60% more calls answered vs. non-AI operators 150M interactions handled, 99.99% uptime Backed by Accel, Atlantic Labs, and Singular. Trusted by 1,000+ customers. Recognized as one of the most promising companies in Germany. Lead VOIP Engineer (FreeSWITCH & Kamailio) Location: Berlin/Remote Job Type: Full-Time Experience Level: Senior About the Role We are seeking an experienced VOIP Engineer with a strong background in FreeSWITCH 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 be responsible for designing, implementing, and optimizing scalable VOIP solutions while ensuring high availability and performance. Responsibilities Design, deploy, and maintain FreeSWITCH and Kamailio-based VoIP solutions. Configure and troubleshoot SIP protocols, RTP streams , and media gateways . Monitor and optimize high-load production FreeSWITCH 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, DevOps, 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. Requirements 5+ years of experience in VOIP engineering, particularly with FreeSWITCH and Kamailio . 3 years of experience with k8s on production systems is a must have. Strong expertise in SIP protocol, RTP streaming, and VoIP call flows . Experience working in high-load production FreeSWITCH 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, PostgreSQL, or NoSQL 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.