Retell AI is using first principles to reimagine the call center with cutting-edge voice AI.
Thousands of companies now utilize Retell’s AI voice agents to handle sales, support, and logistics calls that once required large teams of human agents. Backed by Y Combinator, Alt Capital, and other leading investors, we have scaled to $60M ARR with a team of 40 people, up from $5M at the start of 2025.
Our vision for 2026 is to build a modern CX platform where entire contact centers are powered by AI. Instead of basic automation that needs constant human tuning, we’re creating intelligent AI “workers” that can act as frontline agents, QA analysts, and managers — continuously executing, monitoring, and improving customer interactions.
We’re growing quickly and looking for ambitious builders who want to tackle hard technical problems, move fast, and have real impact at one of the fastest-growing voice AI startups.
Let’s build the future together.
We’re a top 50 AI app in a16z list: a16z Top AI Apps
#4 on Brex's Fast-Growing Software Vendors of 2025: Brex Benchmark 2025
We're also one of the top ranking startups on: Lean AI Leaderboard
Enterprise Tech 30: Wing Venture Capital ET30
We are seeking a Telephony Engineer to who will own the technical success of our telephony integrations, act as the first line of defense for advanced enterprise telephony support, and drive seamless post-onboarding experiences. Your work will directly impact call quality, reliability, and customer experience. You’ll move fast, collaborate with customers, and help define the gold standard for AI voice infrastructure.
KEY RESPONSIBILITIESIntegration Ownership: Manage and collaborate with customers to support complex SIP integrations with CCaaS/CPaaS platforms like NiCE, Five9, Avaya, Genesys, Amazon Connect, Twilio, and Telnyx, while driving future platform integrations.
Advanced Troubleshooting: Investigate and debug call failures via PCAP analysis, SIP traces, and carrier logs to improve reliability.
Enterprise Support Frontline: Act as the primary technical point of contact for enterprise clients post-onboarding.
Product Advocacy: Translate customer technical feedback and friction points into actionable product improvements for our development teams.
Have 5+ years as a Telephony Engineer, VoIP Engineer, or equivalent low-latency networking role.
Have deep understanding of the SIP Protocol (RFC 3261), RTP (media) debugging voice quality issues with PCAPs.
Strong Networking fundamentals.(TCP/IP/TLS, DNS, Firewalls).
Familiarity with modern CPaaS/cloud communication platforms (e.g., Twilio, Plivo, Telnyx).
Ability to write or modify basic scripts (e.g., Python, Bash, JavaScript). Automate routine troubleshooting tasks.
Exceptional ability to guide premium clients through complex setups and communicate technical issues clearly.
Familiarity with Asterisk/FreeSWITCH/Kamailio or relevant SIP proxy / SIP servers is a plus.
Employment Type: Full-Time or Part-Time 1099 Contractor
Location: Remote
Compensation: $6000–$7500 USD/Month, based on experience
Hours: Must be open to working some overlapping hours with our Pacific Time team and customers.
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