Staff Software Engineer - Experimentation

We are looking for a Staff Software Engineer to own how Headway runs experiments. "Ship small, learn fast" is the second principle on the list above, and experimentation is how we actually do it: eleven teams have run hundreds of experiments deciding how patients find a therapist, how quickly new providers get up and running, whether our AI products are working, and how we collect the clinical outcomes data that proves care is effective. You will own the platform all of that runs on. This is a hands-on technical leadership role with unusually wide reach. You will design and build the core primitives, including how users are assigned to experiments, how we record what someone actually saw, and how we recognize the same person across devices and between browsing anonymously and signing in. You will decide what our long-term experimentation and feature flagging stack should be; we run LaunchDarkly and Statsig today, and that architecture is yours to evaluate and consolidate. You will also make AI a real part of the workflow, from validating an experiment's setup before it starts to catching a broken experiment automatically instead of discovering it in a Slack thread a week later. You will also evolve our experimentation capabilities to expand into market-based testing. Headway is a multi-sided marketplace, so we frequently need to change something for therapists and measure what happens to patients, which changes both how a test must be designed and how it can be analyzed. We need to test whole geographic markets, not just individual users. The job is a platform and a program in equal measure. Half of it is the technical foundation. The other half is raising how well the whole company experiments: the defaults, the review, the documentation, and the education that let a team run a trustworthy experiment without needing you in the room. You will gather needs from teams who all want something different, sequence them into a roadmap, and say no clearly, which means acting as part technical product manager for your own platform. You will sit in the Patient org, where the highest volume of experiments happens, and serve the whole company. You will own assignment, exposure, and the experiment data pipelines, which are the parts of the chain that are engineering problems. You will work closely with Data Science, who own statistical methodology, and with the teams who own our event tracking and metric definitions, because a number is only as trustworthy as the weakest link in that chain.

Responsibilities

Own how Headway runs experiments; Design and build the core primitives, including how users are assigned to experiments, how we record what someone actually saw, and how we recognize the same person across devices and between browsing anonymously and signing in; Decide what the long-term experimentation and feature flagging stack should be; Make AI a real part of the workflow; Evolve experimentation capabilities to expand into market-based testing; Raise how well the whole company experiments through defaults, review, documentation, and education; Act as part technical product manager for your own platform; Own assignment, exposure, and the experiment data pipelines; Work closely with Data Science and with the teams who own event tracking and metric definitions

Requirements

Owned an experimentation or feature flagging stack end to end rather than only used one; Built the parts that do not come out of the box: assignment that persists correctly, exposure that reflects what a user actually saw, identity resolved across sessions and devices, or the diagnostics that catch a broken experiment early; Fluent enough in statistics to be a real partner to data scientists; Debugged the hard class of measurement bugs: traffic that split unevenly, users who ended up in both arms, effects that vanished once you looked at who was actually exposed, identity that broke between anonymous and logged-in sessions; Built a program and not only a platform; Made a build versus buy call on a platform and lived with it; Landed a migration on teams that did not ask for one, by making the new path easier than the old path rather than by mandate; Use AI as genuine leverage in your work and have clear opinions about where it must not be trusted without a human; Driven technical direction beyond your own team through design documents, reviews, and planning cycles, and regularly mentor senior engineers; Willing to flex across the stack

Nice to have

Experience with multi-sided marketplaces, growth or search and ranking systems, or healthcare

Benefits

Equity compensation; Medical, Dental, and Vision coverage; HSA/FSA; 401K; Work-from-Home Stipend; Therapy Reimbursement; 16-week parental leave for eligible employees; Carrot Fertility annual reimbursement and membership; 13 paid holidays each year as well as a Holiday Break during the week between December 25th and December 31st; Flexible PTO; Employee Assistance Program (EAP); Training and professional development