Senior Backend Software Engineer (m/f/n)

Currently, for one of our Partners, we are looking for an experienced Senior Backend Software Engineer (m/f/n) to support a long-term eDelivery project delivered for an organization of the European Commission.

Nature of tasks:

• eDelivery Development: Contribute to the development of eDelivery products (Domibus, DomiSMP, DomiSML, eDelivery Conformance Testing Platform) in coordination with Technical Architect(s).

• Backend Development & Testing: Develop and maintain services, write clean, functional, maintainable code, troubleshoot problems, write unit/integration tests, and integrate them into the CI/CD pipeline.

• Distributed Architecture: Design distributed transaction patterns, handle idempotency, duplicate detection, reliable message delivery (at-least-once / exactly-once), eventual consistency, and compensating transactions.

• Security & APIs: Implement authentication/authorization flows, mTLS, secrets management, HSM integration, threat modeling, and versioned REST/SOAP APIs with enforced contracts (OpenAPI, WSDL).

• Messaging & Integrations: Govern inter-service communication patterns, design message broker topologies (queues, topics, dead-letter handling), and integrate via standard protocols (AS4, ebMS3).

• Performance & Data Storage: Optimize for speed and scalability, profile database queries, resolve contention points (connection pools, thread starvation), and design data storage solutions (partitioning, sharding, zero-downtime migrations).

• Observability & Cloud: Implement structured logging, distributed tracing, metrics collection, participate in post-mortems, write technical documentation, and basic configuration of cloud services.

Minimum Requirements:

• Backend languages and frameworks (Java, Jakarta EE, Spring/Spring Boot, Hibernate): at least 8 years.

• Build and dependency management tools (Maven, Gradle, npm): at least 7 years.

• Relational databases (Oracle DB, PostgreSQL, MySQL): at least 5 years.

• REST APIs and/or SOAP/WSDL web services: at least 5 years.

• Message brokers (ActiveMQ, RabbitMQ, Kafka): at least 5 years.

• Message format standards (XML, XSD, XPath, WSDL, JSON, JSON Schema): at least 5 years.

• Git and Git workflows (GitFlow, trunk-based development): at least 5 years.

• Experience with distributed transaction patterns and idempotency: at least 1 year.

• English: minimum B2 level.

Nice to have:

• eDelivery Standards: Experience with core eDelivery standards and profiles: OASIS ebMS3, AS4, SMP, BDXL, ebCore PartyId, and technical standards.

• Security & PKI: Experience with security protocols, web application security, secure API design (TLS/SSL, mTLS, PKI, HTTPS, WS-Security, CSP, SOAP/REST, OAuth 2.0, OpenID Connect, JWT, SAML, OWASP mitigation) and secrets management tools (HashiCorp Vault, AWS Secrets Manager).

• Performance & Code Quality: Experience in JVM profiling, resolving thread contention/connection pool issues, Liquibase/zero-downtime database migrations, code reviews, static analysis (SonarQube), and technical debt management.

• Architecture & Messaging: Experience with standard integration protocols, enterprise messaging patterns, service discovery, circuit breakers, load balancing, and containerization (Docker).

• Tooling & Infrastructure: Experience with CI/CD pipelines (Bamboo, GitLab CI, GitHub Actions), Infrastructure-as-Code (Terraform, Ansible), and monitoring/telemetry tools (Dynatrace, Splunk, Elastic APM, OpenTelemetry).

• Other Skills & Domain: Experience with Python or Node.js, Java software architecture / enterprise software development certifications, working for European institutions, public administration, or large international organizations, and French language skills (B2+).

Offer:

• Type of contract: B2B via SHIMI.

• Rate: 450-500 Eur/MD.

• Type of work: mostly remote work (the candidate must be located within the EU) — occasional travel to Brussels may be required (with at least 7 days' notice).

• Travel: Occasional travel to Brussels may be required. Two planned customer meetings per 12-month period (up to 2 days each) are foreseen and covered by the contractor. Additional travel may be reimbursed only if explicitly requested and approved by the customer.

• Duration of the collaboration: long-term.