Senior Java Developer, Spring Boot, Backend Development, REST APIs, Google Cloud, Modernization

Project overview

For upcoming modernization projects in the mid-sized business sector, we are looking for experienced Java developers (m/f/d) for our expert pool.

A typical project looks like this:

Starting Situation

A legacy business application is being modernized and migrated to Google Cloud. The core of this involves the backend services, which handle business logic, data persistence, and interfaces, and supply the web portal in Angular as well as the mobile app in Flutter via REST APIs. The business logic will be gradually decoupled from the existing system, refactored, and operated as Spring Boot services on Cloud Run or GKE. External systems such as an ERP (e.g., SAP) will be connected via defined interfaces.

Responsibilities

Must-Haves

Desirable

Framework

Application

Please answer briefly:

When communicating via email, please provide the project ID of this advertisement. Telephone contact is only possible after prior appointment.

(Java, Spring Boot, Backend Development, REST, Microservices, PostgreSQL, Google Cloud Platform, Cloud Run, Kubernetes, Docker, CI/CD, Kafka)

Job facts: Direct client project

• Clarify functional requirements with Business Analysts and Product Owners and translate them into technical solutions
• Analyze existing business logic, refactor it, and gradually migrate it into Spring Boot services
• Design and implement REST APIs (OpenAPI), including versioning, error handling, and documentation
• Design data models and persistence with PostgreSQL or Cloud SQL, manage schema changes with Flyway or Liquibase
• Secure authentication and authorization using OAuth2 or OpenID Connect
• Implement asynchronous processing and connection of external systems via Pub/Sub or Kafka
• Write and maintain automated tests (unit, integration, and contract tests)
• Set up CI/CD for build and deployment on Google Cloud, integrate logging, tracing, and metrics
• Conduct code reviews, document technical decisions, and guide developers within the team
• At least 5 years of professional experience in backend development with Java, including at least 3 years with Spring Boot in production applications
• Design and implementation of REST APIs, as well as experience with relational databases (PostgreSQL or comparable)
• Experience with modernizing or replacing legacy applications (monolith to services, migration of business logic)
• Automated testing and CI/CD in daily work (e.g., JUnit, Testcontainers, GitHub Actions or GitLab CI)
• Fluent German, good English
• Operation of services in containers on Google Cloud (Cloud Run, GKE) or another public cloud
• Event-driven architectures (Pub/Sub, Kafka) and integration of ERP systems (e.g., SAP via OData)
• Kotlin, Spring Cloud, Quarkus, or GraalVM
• Security according to OWASP and GDPR-compliant data processing
• Collaboration in agile, distributed teams
• Assignment: predominantly remote, occasional on-site appointments in DACH region
• Duration: typically 4 to 6 months, extension possible
• Utilization: 80 to 100 percent
• Start: project-dependent, from Q1 2027
• Which backend have you most significantly developed recently (purpose, your role, team size, Java and Spring Boot version)?
• How do you ensure quality from requirements to acceptance?
• What is your hourly rate and when are you available?

Project details

• Start: 2027-01
• Duration: 6 Monate
• Remote: hybrid
• Location: BerlinBrandenburg, Deutschland, DE
• Languages: German