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.

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Over 20M hours of operations automated

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60% more calls answered vs. non-AI operators

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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

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Design, deploy, and maintain FreeSWITCH and Kamailio-based VoIP solutions.

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Configure and troubleshoot SIP protocols, RTP streams, and media gateways.

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Monitor and optimize high-load production FreeSWITCH and VOIP systems.

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Implement and manage SIP monitoring tools like Homer or other real-time debugging solutions.

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Develop and fine-tune call routing, failover mechanisms, and load balancing strategies.

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Ensure security, scalability, and redundancy in the VoIP infrastructure.

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Troubleshoot and resolve VoIP-related issues in production environments.

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Collaborate with development, DevOps, and support teams to improve system performance.

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Work with SIP Trunks, SBCs (Session Border Controllers), and Media Servers.

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Implement WebRTC-based voice and video solutions.

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Document system configurations, troubleshooting guides, and best practices.

Requirements

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5+ years of experience in VOIP engineering, particularly with FreeSWITCH and Kamailio.

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3 years of experience with k8s on production systems is a must have.

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Strong expertise in SIP protocol, RTP streaming, and VoIP call flows.

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Experience working in high-load production FreeSWITCH environments.

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Hands‑on experience with Homer SIP capture or similar SIP monitoring tools.

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Deep understanding of NAT traversal, STUN/TURN, WebRTC, and ICE frameworks.

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Strong knowledge of load balancing, failover strategies, and traffic optimization.

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Proficiency in Linux administration, networking, and troubleshooting.

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Experience with database integration (Redis, PostgreSQL, or NoSQL solutions).

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Familiarity with WebRTC, Asterisk, OpenSIPS, or RTP Proxy is a plus.

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Ability to write Bash/Python (or Golang) scripts for automation and monitoring.

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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.