Base Salary
$175k - $195k/yr
Responsibilities
- Own Tin Can’s production SIP and media plane, including Kamailio, FreeSWITCH, and carrier trunking.
- Review call-path changes and author SIP test scenarios that gate voice changes before release.
- Write and maintain Kamailio routing logic, including dispatcher, registrar, usrloc, htable, DMQ replication, and TLS configuration.
- Build FreeSWITCH dial plans and integrations using ESL, mod_xml_curl, Lua, and Sofia profiles.
- Measure and operationalize call quality metrics including MOS, jitter, packet loss, and setup time.
- Model and load-test concurrent calls, calls per second, and trunk capacity against peak demand.
- Extend the SIP and media layer into new countries with market-specific codec and emergency-calling requirements.
- Harden signaling and media using SIP over TLS, SRTP, rate limiting, toll-fraud prevention, and topology hiding.
- Improve team fluency through documentation, runbooks, and technical reviews.
Requirements
- 5+ years of experience building and operating real-time voice systems in production.
- Hands-on depth with Kamailio and FreeSWITCH.
- Strong knowledge of SIP and RTP, including location services, dialog state, transfers, Path routing, NAT traversal, and late-packet media behavior.
- Ability to debug live production calls from packet captures and SIP traces through root cause and resolution.
- Experience treating configuration as code and infrastructure as reproducible.
- Fluency using AI for diagnosis, analysis, and testing.
- Clear written and verbal communication skills and a collaborative, low-ego working style.
- Preferred experience with rtpengine, Homer/HEP, SIPp regression suites, Prometheus exporters, STIR/SHAKEN, or carrier interconnect.
- Additional preferred experience with WebRTC internals, including ICE, DTLS-SRTP, and TURN, and with bridging WebRTC to SIP.
Benefits
- Opportunity to build technology intended to give children a safer, more analog way to connect.
- End-to-end ownership of Tin Can’s voice call path and its technical direction.
- Small, high-trust, mission-driven team with room to explore and challenge assumptions.
About Tin Can
Tin Can is a screen-free phone for kids that gives them the independence to call friends and family—without giving them a smartphone. Built like a modern landline, Tin Can connects over Wi-Fi and uses a simple mobile app for parents to control who can call in and out. There’s no browser, no app store, no camera, no spam—just voice. It’s a safer, saner way for kids to communicate and gain a bit of freedom without the baggage of adult tech. We believe that real connection doesn’t require a screen. And that childhood is better when it’s full of imagination, not notifications. Tin Can started in one neighborhood in Seattle, where we hand-installed 40 early prototypes and watched them spread by word of mouth. Now, Tin Can is being used by kids in over 30 states—with no marketing, no paid ads, just families telling other families. We’re growing fast, and so is the movement of parents looking for a better way to let their kids be independent, without handing over the internet in their pocket. Our newest Tin Can is fully custom hardware, designed from the ground up to be beautifully simple. It works out of the box, connects through our app, and comes with smart features like emergency calling, quiet hours, and a free Can2Can plan that lets any two Tin Cans call each other with no subscription required. Tin Can is built for the 4–13 age range—when kids are old enough to want a phone, but not quite old enough to manage one. We’re on a mission to bring back the freedom of the old-school landline, updated for today’s families.