Java 21 / React Developer (Spring Boot + TypeScript) — Circular Economy — Paris

Abbeal is looking for a Java 21 + React/TypeScript developer to join a product team building the core platform of a circular-economy player, on a regulated extended producer responsibility scheme. A serious technical environment: 15 Spring Boot microservices, micro-frontend applications and GCP infrastructure.

The context

The platform handles contracting, declarations, eco-contributions and pricing scales for a recycling scheme. The business domain is rich and regulated: understanding the rule before writing the code is part of the job, not an afterthought.

On the technical side the project owns its standards: hexagonal architecture and DDD across several services, several hundred Flyway migrations in production, and one rule that is not up for discussion — no change without a test.

The role

• Build and evolve Spring Boot microservices in Java 21, with strict separation between domain, use cases, SPI ports and infrastructure adapters
• Contribute equally to React 18/19 TypeScript frontends in an NX monorepo with module federation — this is a genuine 50/50 back and front role
• Work the PostgreSQL data model, native SQL included, and version schemas with Flyway
• Write the tests that go with it: unit, feature and integration against a real database
• Turn regulated functional requirements into technical design, and push back when they do not hold
• Ship small, tested Merge Requests that stay within the agreed scope

What we are looking for

• 3 to 4 years of hands-on development experience. That level is deliberate: this role is not open to very senior profiles
• Solid Java 21 in production. Kotlin is not required — it is a plus, not a prerequisite
• React 18/19 and TypeScript in production. Non-negotiable: the frontend carries as much weight as the backend here
• Spring Boot 3.4 / Spring 6: Web, Data JPA, Security, Cloud
• JPA / Hibernate 6 and PostgreSQL, with real SQL fluency
• NX monorepo and module federation, TanStack React Query, React Final Form, react-intl
• Testing: JUnit 5 and AssertJ on the backend, Jest and Testing Library on the frontend. Non-negotiable on this project
• Git, GitLab CI, Agile with JIRA
• Fluent French is required: part of the code, tests and documentation are written in French, and ceremonies are held in French
• Based in the Paris region and available for 2 days a week on the client site
• Available from 28 September 2026

Nice to have

• Kotlin — the project's historical language, but no longer a condition for the role
• DDD and hexagonal architecture
• Docker multi-stage builds and GCP: App Engine, Cloud Run, Cloud Storage, Pub/Sub
• Asynchronous messaging such as RabbitMQ or Kafka, transferable to Pub/Sub
• Cucumber / BDD, with Gherkin scenarios written in French
• Third-party API integration: e-signature, public registries, CRM, banking flows
• Feature flags (Unleash), SonarQube, JaCoCo, Cypress
• Terraform / Ansible, application security with JWT and fine-grained profile permissions

Conditions

• Freelance, up to EUR 500/day — the client budget is firm at that cap
• 3-month renewable assignment, starting 28 September 2026
• Paris, hybrid: 2 days a week at the client's offices near Gare de Lyon, the rest with the team
• 1 to 2 remote days a week once up to speed and autonomous