Senior Java Developer (Platform Modernization)

Addepto; Warszawa; On-site; PLN 180,000 - 240,000; Full time

Job summary

Addepto is seeking a Senior Java Developer to join a modernizing, cloud-native platform project. You will implement backend services with Java and Spring Boot, rework legacy logic, and ensure production readiness with automated tests and CI/CD.

You will work on Azure-based services, PostgreSQL data layer, and data migration tooling, contributing to a platform that supports real-time operations and analytics across large datasets.

Qualifications

• Strong experience with Java and Spring Boot in enterprise environments.
• Ability to analyze legacy Java/Spring code and rewrite business logic with tests.
• Experience building REST APIs and data migration tooling across Oracle and PostgreSQL.

Responsibilities

• Design and implement backend services in Java/Spring Boot across domains.
• Migrate data and functionality from Oracle to PostgreSQL in a scalable way.
• Develop REST APIs (OpenAPI) consumed by portals and integrations.

Skills

Java

Spring Boot

OpenAPI

REST APIs

JUnit

Testcontainers

CI/CD

Azure

Kafka

JPA/Hibernate

Tools

Oracle

PostgreSQL

Databricks

Flyway

Liquibase

Azure Service Bus

Job description

Addepto is a leading AI consulting ( https://addepto.com/ai-consulting/ ) and data engineering ( https://addepto.com/data-engineering-services/ ) company that builds scalable, ROI-focused AI solutions for some of the world's largest enterprises and pioneering startups, including Rolls Royce, Continental, Porsche, ABB, and WGU. With an exclusive focus on Artificial Intelligence and Big Data, Addepto helps organizations unlock the full potential of their data through systems designed for measurable business impact and long-term growth.

The company's work extends beyond client engagements. Drawing from real-world challenges and insights, Addepto has developed its own product - ContextClue - and actively contributes open-source solutions to the AI community. This commitment to transforming practical experience into scalable innovation has earned Addepto recognition by Forbes as one of the top 10 AI consulting companies worldwide .

As part of KMS Technology , a US-based global technology group, Addepto combines deep AI specialization with enterprise-scale delivery capabilities—enabling the partnership to move clients from AI experimentation to production impact, securely and at scale.

We are modernizing a large, business-critical operational platform that has evolved over many years and combines application logic, database-level rules, and partly manual operational processes. The project involves transitioning the existing solution towards a modern, cloud-native architecture , delivered by a small senior team working with heavy AI leverage.

As a Senior Java Developer , you will join the team at the moment when requirements and target architecture are in place and the build starts. This is a hands-on implementation role — the large majority of your time goes into writing, testing, and shipping production code, not into high-level design or governance.

Here is what the project involves:

• Re-implementing legacy logic. Working through existing Java/Spring code, Oracle schemas, and PL/SQL, extracting the business rules that actually run the operation, and rebuilding them as clean, well-tested Spring Boot services.
• Building the new platform on Azure. Implementing services, integrations, and APIs on Azure with PostgreSQL as the operational database and Databricks for analytics and reporting data.
• Migrating without stopping operations. Moving data and functionality from Oracle to the new stack in a way that supports parallel run, reconciliation, and a safe cutover for a system that cannot go down.

Your main responsibilities:

• Design and implement backend services in Java and Spring Boot, from domain model and business logic through persistence and API layers.
• Analyze legacy Java/Spring code and Oracle PL/SQL, and re-implement business logic in the new services, with tests that prove behavioural parity.
• Build the PostgreSQL data layer: schema design, JPA/Hibernate mappings, versioned migrations (Flyway / Liquibase), and query performance tuning.
• Implement Oracle PostgreSQL data migration and reconciliation tooling to support parallel run and cutover.
• Develop REST APIs (contract-first, OpenAPI) consumed by operational portals and integrated systems.
• Implement asynchronous integrations and event flows (e.g. Azure Service Bus, Kafka), including retries, idempotency, and error handling.
• Deliver data feeds from the operational platform into Databricks in cooperation with data engineers.
• Write automated tests at every level (JUnit, integration tests with Testcontainers, contract tests) and keep the codebase production-ready.
• Contribute to CI/CD pipelines, containerization, and deployment to Azure across DEV / TEST / PROD environments.
• Build in logging, monitoring, and alerting so the system can be run 24/7; take part in troubleshooting and production readiness ahead of go-live.
• Work closely with the Business Analyst / Product Owner on user stories and acceptance criteria, and do code reviews within the team.