Senior VoIP Engineer

Uncover; Seattle, Northern (WA, KY); Hybrid; USD 140,000 - 210,000; Full time

Job summary

Tin Can is hiring a Senior VoIP Engineer to own the SIP and media stack across Kamailio, FreeSWITCH, and carrier trunks. You’ll ensure calls connect, sound clear, and scale as we grow. You’ll write test scenarios, tune routing, and push reliability end-to-end.

You’ll work on TLS/SRTP hardening, NAT traversal challenges, and load-testing for peak holidays. You’ll document workflows and mentor teammates, shaping our voice platform.

Qualifications

• 5+ years building and operating real-time voice systems in production.
• Deep hands-on experience with Kamailio and FreeSWITCH.
• Proficient with SIP, RTP, NAT traversal, and media handling.
• Experience debugging live calls from packet captures and SIP traces.
• Treats config as code and infrastructure as reproducible.
• Fluent with AI as a multiplier in diagnosis and testing.
• Clear written communicator and collaborative mindset.

Responsibilities

• Own production SIP and media plane end to end, including Kamailio and FreeSWITCH.
• Review call-path changes and author SIP test scenarios.
• Write Kamailio routing logic, including TLS and NAT handling.
• Build FreeSWITCH dialplans and integrations.
• Provide packet-level call quality metrics and alerting.
• Model and load-test call capacity for peak demand.
• Extend SIP/media layer to new markets as needed.
• Harden signaling and media paths for security and reliability.
• Document runbooks and reviews to keep stack understandable.

Skills

Real-time voice systems

Kamailio

FreeSWITCH

SIP/RTP depth

Call-path debugging

Infrastructure as code

AI in engineering

Clear communication

Team collaboration

Tools

Kamailio

FreeSWITCH

ESL

mod_xml_curl

Lua

Sofia profiles

TLS/SRTP

Job description

About Tin CanTin Can is building a safer, simpler way for kids to connect — without smartphones. We’re creating screen-free, delightful devices and services that let families call the people who matter most, free from the noise of today’s digital world.We’re building a bold, authentic, nostalgic, and kinda quirky brand that resonates with folks who want something simpler & better for their kids than the tech-infused lives we’re currently living (and who have a sense of humor about it). As we gear up to scale to thousands of families, we’re ready to bring on an engineer to help make it happen.

The Role

A call either connects or it doesn’t — there’s no partial credit when a kid picks up a Tin Can to reach Grandma, or to dial 911. We’re hiring a Senior VoIP Engineer to own the SIP and media plane that carries every one of those calls: how it routes, how it sounds, and how we know it works. It’s the first role dedicated entirely to that stack.

What You’ll Do

• Own our production SIP and media plane end to end — Kamailio, FreeSWITCH, and the carrier trunking behind every call to the outside world
• Be the reviewer of record for call-path changes, and author the SIP test scenarios that gate a voice change before it ships
• Write and maintain the Kamailio routing logic behind every call — dispatcher, registrar and usrloc tuning, htable, DMQ replication, TLS
• Build FreeSWITCH dialplans and integrations (ESL, mod_xml_curl, Lua, Sofia profiles), and keep call state correct across boxes, transfers, and NAT
• Produce the packet-level truth about call quality — MOS, jitter, packet loss, setup time — and make it trustworthy enough to alarm on
• Model and load-test call capacity — concurrent calls, calls per second, trunk headroom — against our holiday peak, using scenarios built on real call flows
• Extend the SIP and media layer into new countries as we expand, where codec support and emergency-calling rules change market to market
• Harden the signaling and media path: SIP over TLS, SRTP, rate limiting, toll-fraud prevention, and topology hiding
• Raise the team’s voice fluency: the documentation, runbooks, and reviews that make this stack legible to every engineer here

What We’re Looking For

• 5+ years building and operating real-time voice systems in production, with hands-on Kamailio and FreeSWITCH depth
• You can hold your own on SIP and RTP: location services, dialog state, transfers, Path routing, NAT traversal, and what happens to media when a packet arrives late
• You’ve debugged live production calls from a packet capture and a SIP trace to root cause
• You treat config as code and infrastructure as reproducible
• Fluency using AI as a multiplier across diagnosis, analysis, and testing
• A clear communicator who writes things down
• A collaborative, low-ego approach — everyone here sweeps the floor

Bonus: rtpengine, Homer/HEP for capture and call-leg correlation, SIPp regression suites, Prometheus exporters for the voice plane, or STIR/SHAKEN and carrier interconnect

Extra bonus: WebRTC internals (ICE, DTLS-SRTP, TURN) and bridging WebRTC to SIP

Why Join Tin Can

We’re building tech that protects childhood: We’re on a quest to give kids a more analog childhood — one with real conversations, real connection, and way less screen time. No doomscrolling, data mining, or dopamine traps — just a simpler, better way for kids to stay in touch. This is a rare opportunity to build something that truly matters.

You’ll own the call path outright: This is the first role dedicated entirely to our voice stack — the systems that decide whether a kid’s call connects and how it sounds. You’ll set the direction for how calling works as we scale.

Small, high-trust team: Every company says “team,” but at Tin Can it means something different. We’re a small, mission-driven group that genuinely has each other’s backs — professionally and personally. You’ll be joining a tight-knit crew where your ideas and instincts matter from day one.

Room to explore, not just execute: You’ll have the space to challenge assumptions, solve hard problems, and build systems that reflect our values of trust, simplicity, and care.

If you’re excited by the idea of owning the systems that carry a kid’s voice to the people who matter most, and making them so dependable that nobody has to think about them, we’d love to meet you.