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# Senior JavaScript Engineer - Website, Booking Flow & Internal Tools

- **Company:** Colonies
- **Location:** Paris, France
- **Experience:** Expert
- **Contract:** Permanent contract
- **Skills:** JavaScript (Programming Language), A/B Testing, Application Programming Interfaces (APIs), Cursor (Graphical User Interface Elements), Electronic Signatures, Next.js, TypeScript, ReactJS, Automation Anywhere
- **Published:** September 29, 2026
- **Apply:** https://www.indeed.com/viewjob?jk=7651862e1cc2de42

## About the Role

Languages: French and English, fluent written and spoken, * 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.

## Description

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.


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