Software Engineer 3 (SDE3)

About this Role

This is a backend-leaning fullstack role with a large surface area. The role carries as much product responsibility as technical: you’re expected to have a view on what should be built, not only on how. It is also deeply hands-on — you’ll ship code every week, and you’ll be the person others check with before doing something costly.

Engineering at KC

We are building an AI-native engineering team around small teams and unusually large ownership. AI is making writing software dramatically faster; we think this should increase the scope of engineers, not reduce it. Engineers at KC are expected to understand the user and the business, question what should be built, make product and technical decisions, use AI aggressively, and own the outcome in production — not just the code.

What you will do:

• Own a technical domain spanning multiple services — its architecture, reliability, performance, cost and roadmap.
• Set technical direction through design docs, technology choices, service boundaries and interface design, and be right often enough that people stop second-guessing you.
• Lead complex projects end to end, from problem framing and architecture through rollout, measurement and iteration.
• Shape what gets built, not just how — challenge requirements, propose alternatives, and be willing to argue that the highest-value version of a feature is a smaller one.
• Raise the quality bar through code review, testing and eval strategy, and the guardrails that let a small team ship a large volume of code without breaking things.
• Drive down incidents, latency and infrastructure cost in the systems you own, and know which of the three matters most this quarter.
• Mentor SDE 1s and SDE 2s, and make the engineers around you measurably better — faster ramp-up, better designs, fewer repeated mistakes.
• Define how AI tooling is used in your domain: which parts of the system are fine to generate and throw away, which get built carefully by hand, and what the test layer must catch before anything reaches production.

What we are looking for:

• 5+ years of experience, including significant time as the technical owner of a system in production — long enough to have lived with your own decisions.
• Depth in backend engineering: distributed systems, data modelling at scale, performance and reliability under real load.
• Strong product thinking. You can look at a roadmap item and tell us what’s worth building, what isn’t, and what the cheap version that answers the same question looks like.
• Enough frontend experience to build an interface yourself when needed is a plus.
• Experience designing systems that other engineers build on top of, and evidence they were pleasant to build on.
• Sophisticated use of AI coding tools, with well-formed opinions on architecture, review and testing in a codebase where much of the code is generated.