Software Engineer Java / Spring - Freelance (M/F)

About the role

Daily rate (TJM): 460€/day CONTEXT Within the extended supply chain of a large company, our digital solutions are transforming to meet the challenges of expanding our service and product offerings and optimizing our logistics chain. You will join a team structured around two main products: * a connector responsible for the creation, management, and tracking of B2B orders within our ERP. The connector is used by all of the company's digital products that need to create B2B orders. * a solution that identifies the most relevant warehouse for replenishing an item to a given store. These solutions are at the heart of our Supply ecosystem and play a key role in its transformation. In a context of accelerating wholesale and franchise strategies, as well as the development of new use cases related to the circular economy, they will experience significant growth in the coming years. This evolution is accompanied by large-scale deployment, with the integration of new partners, an increase in the number of users, and sustained business growth. Our current team consists of 7 people including 2 product managers, 4 developers, and 1 support engineer. MISSIONS Context & Challenges The application base is in an active phase of deployment and scaling. The mission entrusted to the external Backend Software Engineer revolves around two main axes: Backend Development, Evolutions & Consolidation (Build) * Work in close collaboration with the Product Manager to analyze, refine, estimate, and implement business requirements. * Design, develop, and test robust microservices. Consolidate the existing base (refactoring, reducing technical debt). * Participate in software design choices and microservices architecture reflections to lead the base toward full maturity. * Optimize asynchronous data exchanges via Kafka and data persistence (PostgreSQL / MongoDB). Software Quality, Tests & CI/CD * Secure the base by strengthening automated test coverage (Cucumber, unit tests, integration/API tests). * Perform systematic and constructive code reviews within the backend team. * Participate in the evolution and monitoring of CI/CD pipelines (GitHub Actions, Docker, Kubernetes, Helm). Technical Documentation * Write and maintain backend documentation (REST API contracts, service architectures, Kafka event flows). L3 Support, Performance & MCO (Run) * Diagnose deployment anomalies, execute load/performance tests, and ensure the reliability of the base in production in conjunction with the Run team. Level 3 Support & Anomaly Analysis * Diagnose and correct complex incidents and Backend regressions of Level 3 transferred by the Run team. * Identify the Root Causes of deployment instabilities to provide lasting fixes. Performance Tests * Design, script, and execute load, stress, and scalability tests on Java/Spring Boot APIs and microservices. * Analyze Backend behavior under heavy load (Kafka topic throughput, REST API response times, SQL/NoSQL queries, CPU/JVM consumption). * Identify bottlenecks, memory leaks (JVM heap memory leaks), or database locks, and implement necessary optimizations. Observability & Monitoring * Set up and enrich backend monitoring (Datadog, Micrometer/Actuator metrics, logs) to proactively detect drifts and anomalies in production. TECHNICAL STACK * Back: Java 17+, Spring Boot. *