Telephony/VOIP Engineer
About the job
- Have 5+ years of experience as a Telephony Engineer, VoIP Engineer, or in an equivalent low-latency networking role.
- Have a deep understanding of the Session Initiation Protocol (SIP; RFC 3261) and Real-time Transport Protocol (RTP), including debugging voice-quality issues with packet captures (PCAPs).
- Have strong networking fundamentals, including TCP/IP, Transport Layer Security (TLS), Domain Name System (DNS), and firewalls.
- Have familiarity with modern CPaaS or cloud communication platforms such as Twilio, Plivo, or Telnyx.
- Be able to write or modify basic scripts in Python, Bash, or JavaScript to automate routine troubleshooting tasks.
- Be able to guide premium clients through complex setups and communicate technical issues clearly.
- Own the technical success of telephony integrations and collaborate with customers to support complex SIP integrations with CCaaS/CPaaS platforms such as NiCE, Five9, Avaya, Genesys, Amazon Connect, Twilio, and Telnyx, while driving future platform integrations.
- Investigate and debug call failures using PCAP analysis, SIP traces, and carrier logs to improve reliability.
- Act as the primary technical point of contact for enterprise clients after onboarding.
- Translate customer technical feedback and friction points into actionable product improvements for development teams.
- Have familiarity with Asterisk, FreeSWITCH, Kamailio, or relevant SIP proxies or SIP servers.
About the company
Retell AI builds AI voice agents that answer and make phone calls for businesses, covering support, scheduling, sales, and payment calls once handled by human agents. Its agents take calls for companies such as CVS Health, Lenovo, Grab, and the San Antonio Spurs, in fields from healthcare to insurance and finance. Businesses build an agent in a drag-and-drop editor or with code, pick the AI model and voice behind it, connect it to phone lines and tools such as calendars, and test it on simulated calls before going live. Customers pay for each minute their agents spend on the phone. Retell AI was founded in 2023, went through the Y Combinator startup program, and is based in Redwood City, California.
Company Size
51-200
Company Stage
Seed
Total Funding
$4.7M
Headquarters
Redwood City, California
Founded
2023
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Simplify's Take
What believers are saying
- Sales doubled in ten months: Retell says its yearly revenue pace hit $80 million by September 2026, from $40 million.
- Room to grow: Retell listed 27 open roles in October 2026, paying senior engineers $200,000 to $300,000 plus equity.
- Jobs don't hinge on fundraising: Retell says it was profitable by November 2025 after one $4.6 million seed round.
What critics are saying
- A better-funded rival is scaling: customer-service AI firm Parloa raised $350 million in January 2026 and aims for 600 staff.
- One voice supplier competes with it: ElevenLabs' agents handled 15 million conversations a week by September 2026, triple February's pace.
- Expect a heavy, in-person load: about 50 employees serve thousands of business customers, mostly from a Redwood City office.
What makes Retell AI unique
- Its call data doubles as a yardstick: Retell's August 2026 test ranked 27 AI models on real contact-center calls.
- Five co-founders run it together: four came from TikTok's parent ByteDance, Google or Meta.
- Its call volume is large for a startup: its agents handled over 55 million calls a month by June 2026.
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Benefits
Health Insurance
Wellness Program
Phone/Internet Stipend
Remote Work Options
Hybrid Work Options
Growth & Insights and Company News
6 month growth
↑ 0%1 year growth
↓ -1%2 year growth
↓ -3%VoiceAIWrapper has launched a white label platform enabling agencies to resell Retell AI voice agents under their own branding. The platform provides client portals on custom domains, workspace management, reporting, and Stripe billing integration. The Dubai-based company addresses the gap between creating voice agents and delivering them to clients. Agencies can set their own pricing through recurring plans, usage packs, or one-time fees. VoiceAIWrapper charges a flat monthly fee without adding per-minute markups to Retell AI usage. The platform supports 11 languages and integrates with tools including GoHighLevel, HubSpot, and Twilio. It also accommodates multiple voice AI providers such as Vapi, ElevenLabs Agents, and Bolna. Plans start at $79 monthly for five client accounts, with a seven-day trial available. Over 1,000 agencies have used the platform. VoiceAIWrapper holds SOC 2 Type 2 certification and complies with GDPR and HIPAA regulations.
Retell AI, a voice AI platform, has launched Conductor, the first graph-native review system for production voice agents. The AI copilot helps enterprises identify failures, automate testing and continuously improve voice agents for contact centers. Conductor operates within agent workflows, displaying proposed changes directly in the interface and requiring human approval before implementation. Users interact with the system in plain English, enabling teams to shape voice agents without coding. The platform already generates 70% of Retell's simulation tests and executes half of all agent edits. The system features a graph-native review interface, operational intelligence for analysing failed calls, and embedded best practices from thousands of enterprise deployments. Retell AI processes over 30 live calls per second and handles 55 million AI phone calls monthly. Conductor is now available to all Retell customers.
Retell AI, a voice AI platform based in Redwood City, California, has been ranked number one on the San Francisco Business Times' 2026 Best Places to Work in the Bay Area list in the 10-24 employees category, scoring 99.04. The recognition comes as the company has grown annual recurring revenue from $10 million to $60 million over the past year whilst maintaining a lean team. Retell AI's workplace culture emphasises autonomy and outcomes over hours worked, with employees able to work remotely for up to two weeks annually. The company's no-code platform enables enterprises to deploy AI voice agents rapidly. It currently processes over 55 million AI phone calls monthly for clients including the San Antonio Spurs, Motorola and Lenovo, handling more than 30 concurrent calls per second at peak volume.
Retell AI, an AI voice agent platform, has been named to Wing VC's Enterprise Tech 30 2026 list, recognised as one of 10 early-stage companies. The list, compiled with Newcomer, highlights voice AI as a key trend for 2026. Launched in 2024, Retell AI reached $50 million ARR in 2025 and now powers over 50 million AI phone calls monthly. The platform enables corporate call centres to deploy AI voice agents for sales and support across multiple channels, offering human-standard voice quality, sub-600ms latency, and support for over 50 languages. The company's technology allows businesses to build and deploy voice AI agents within days rather than the industry standard of a year or more. Retell AI is HIPAA, SOC2 and GDPR compliant.
Evie Wang, co-founder and chief marketing officer of Retell AI, has been named to Inc.'s 2026 Female Founders 500 list. The annual honour recognises the most dynamic women business leaders in the United States, with this year's honourees collectively generating approximately $12.3 billion in 2025 revenue. Wang led Retell AI's marketing and product strategy during a period of hypergrowth, scaling annual recurring revenue from $8 million to $36 million in eight months across a 21-person team. The AI voice agent platform now handles over 40 million real-time calls monthly for Fortune 500 clients and has achieved over 300% quarter-over-quarter user growth. Under Wang's leadership, Retell AI has been recognised as an a16z Top 50 AI company.