Principal Full Stack Engineer

OverviewAs a Principal Full Stack Engineer, you’ll lead a team to build-out Phia’s core product and platform from the ground up. You’ll own engineering execution across frontend, backend, and infrastructure, setting the technical direction while scaling teams that move fast and ship reliably. This is a hands-on leadership role for someone who thrives in ambiguity, partners tightly with Product and Design, and knows how to balance speed, quality, and long-term architecture. You’ll define how engineering works at Phia as we grow from zero to one and beyond.About PhiaPhia has raised $43M from Notable Capital, Khosla Ventures, and Kleiner Perkins to build the AI alignment layer for commerce. In under a year, Phia’s consumer shopping agent has surpassed one million users and partnered with 6,200+ retail brands, representing billions in annual gross merchandise volume. Each month, Phia drives millions of dollars in sales for brands and has achieved 11× revenue growth since launch.In an era where AI vertical agents are reshaping every industry, commerce is on the verge of a complete transformation. Phia is reinventing shopping from a fragmented, impersonal experience into one that feels intelligent, trusted, and built around each user’s intent. This foundation of trust is our wedge to become the end-to-end shopping destination for the next generation of buyers.Phia is a lean, high-ownership team building at startup speed. If you want to ship at high velocity and solve complex problems in consumer AI and commerce, this is the place to do it.What You OwnOwn engineering execution end to end across frontend, backend, and infrastructureDefine technical direction and architecture while moving fast in a zero-to-one environmentBuild, lead, and scale high-performing full-stack engineering teamsPartner closely with Product and Design to turn ideas into shipped, high-quality productDrive engineering decisions in ambiguous problem spaces and unblock teams to maintain velocityEstablish engineering standards, processes, and tooling that support rapid iteration and reliabilityBalance short-term speed with long-term scalability, security, and maintainabilityStay close to the work — reviewing designs, guiding technical decisions, and mentoring leadersOwn production health, performance, and operational excellence as the product scalesQualifications5+ years of engineering experience, including senior leadership roles building and scaling product teamsStrong full-stack background with hands-on experience across frontend, backend, and modern infrastructureProven track record leading engineering in fast-growth, zero-to-one or early-scale environmentsDeep understanding of system design, distributed systems, and scalable architecturesExperience partnering closely with Product and Design leaders to drive product executionAbility to operate at speed in highly ambiguous environmentsClear, direct communicator with strong technical judgment and influence across functions