Staff Software Engineer

Staff Software EngineerAbout the company: Well-funded NYC AI startup building a behavior model that predicts how online shoppers decide. Its AI runs live experiments on eCommerce stores to lift conversion. Small team, direct work with the founders, 4 days/week in Midtown.Why join: Every day, millions of people decide whether to buy something online, and the reasons behind those decisions are still mostly guesswork. The company is working to quantify human psychology: to build an embedding model for human behavior that understands how people react to a page, a price, or a single sentence, and can predict what will work before anyone runs a test. Every experiment the AI runs on a live store teaches that model something about how people decide. The goal is for any company to be able to ask, "I'm selling product X to audience Y, how do I optimize for Z?" and get an answer it can trust. The company is early and well funded. The people who join now will pick the tools, design the models, and help choose who joins next.What you'll work on:The experiment engine. Design the next version of the system that runs every experiment, from the moment the AI has an idea to the final result. It has to stay fast, observable, and reliable at tens of millions of events a day.Agentic AI in production. Build the systems that let the AI look at a store, decide what to test, and put real changes live, with checks that catch mistakes before any shopper sees them.The data behind the model. Decide how event data is collected and shaped so the behavior model can learn from it.How the team builds. Write the design docs, set the engineering principles, and help the engineers around you grow through code review and pairing.Stack: mostly Python on serverless AWS, JavaScript on the frontend, and Postgres alongside ClickHouse.You'll love this job if:You want to design a system from the ground up and live with your decisions.You like making hard technical calls and writing them down so others can build on them.You enjoy making the engineers around you better, and you still want to write code yourself.You can tell when a problem needs a careful design and when it needs a prototype by Friday.You're curious about AI systems that learn and adapt, and you want to see one work on real shoppers.What you bring:8+ years of experience designing and shipping production systemsYou've designed distributed systems that handle a lot of data: event-driven services, streaming pipelines, or data-heavy backends.You've been a tech lead or staff engineer. You've written the design docs, reviewed other people's designs, and set the standards a team follows.You're strong in Python and comfortable with AWS and JavaScript, from the backend to the frontend.You can explain a complex system simply, in writing and out loud.Bonus: experience with ClickHouse, LLMs or agents in production, eCommerce or analytics infrastructure, or building a product from zero at a startup.Values:Curiosity and excellence: Asking questions is the job. The team pushes on each other's ideas, and a failed experiment teaches as much as a winning one.Whatever it takes: If something needs doing, whoever can do it does it, whatever their title.Ownership: Shipping something is where the work starts. You follow it all the way to the result.Agility: Most ideas go from whiteboard to working prototype in two or three days.Enjoy the ride: Building something new comes with rough weeks. The team gets through them together.What's offered:Base salary $190K - $260K plus meaningful equityMedical, dental, and vision for you and your familyUnlimited PTOTax-free commuter and parking benefitsOffice-first culture (4 days/week) in Midtown ManhattanWork directly with the founding teamFree One Medical membership401k