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.