Senior JavaScript Engineer — Website, Booking Flow & Internal Tools

Location: Paris, or remote within France (regular office visits required)

Contract: CDI, full time

Start: ASAP

Languages: French and English, fluent written and spoken

About Colonies

Colonies is on a mission to solve housing. We build and manage flexible living spaces across Europe. Our tech team is small by design: a few people with a lot of leverage, working close to the business. We ship fast and let results decide. What works gets hardened and scaled; what doesn't gets cut.

The role

You will own livecolonies.com end to end. Your first job is to rebuild it: drop the Storyblok CMS from our Next.js stack, redesign, and build it to convert. You’ll help pick the stack: components, libraries and frameworks. From there you own our landing pages (large-project launches, campaigns, experiments) and run A/B tests in PostHog to prove what works.

You will also take ownership of our autonomous booking flow, the first of its kind in the industry. A prospect goes from listing to signed lease and payment without a human in the loop, which means deep integration with our CRM, internal API, document verification, e-signature and payments. The next step is full autonomy on the ops and back-office side as well as the lead side, and extending it well beyond the happy path. You will take it there.

Over time the scope widens: you take the lead on our n8n servers and workflows, contribute to our back-office front-end apps (React/TypeScript), and collaborate on AI workflows such as LangChain/LangGraph integrations.

You will occasionally work with a design agency. Most of the time you will not, so design judgment matters as much as engineering fundamentals.

Who you are

• Senior JavaScript/TypeScript engineer with a proven, demonstrable track record. Show us what you have shipped.

• Expert-level React and Next.js, with real experience in site performance, SEO and conversion optimisation.

• Comfortable building and hardening multi-system integrations where state lives in several places and edge cases are the norm.

• Strong bias for action. You scope, decide and ship without being handed a finished spec.

• Comfortable in a start-up with complex, changing stakeholder requirements.

• You run your own projects: scoping, sequencing, keeping stakeholders informed.

• Fluent with AI coding tools (Claude Code, Cursor or similar) as part of your daily workflow.

• Design-sensitive: you can take a page from brief to polished without a designer.

• Experience with PostHog (or similar) experimentation, and ideally n8n or comparable automation tooling.

What we offer

Real impact and ownership over a product surface the whole company depends on. A high degree of autonomy, earned over time. Autonomy is not isolation: you join a small senior team that works closely together, no Scrum ceremonies, no Sprints, pragmatic project management via Linear, regular syncs to share what we're learning and unblock each other. We care about our craft and keep pace with a fast-moving ecosystem, AI tooling included. Full benefits per

Process

1. HR screening

2. Interview with the future manager

3. Fit interview with 2 team members

4. Final interview with a member of the leadership team