Senior Java Developer (Platform Modernization)

Addepto; Warszawa; Hybrid; PLN 210,000 - 320,000; Full time

Benefits offered by this job

Flexible work arrangements

Career development & training

Medical & wellness benefits

Job summary

Addepto is seeking a Senior Java Developer to join a small, senior team modernizing a large operational platform on Azure. You will re-implement legacy logic, build Spring Boot services, and migrate data from Oracle to PostgreSQL while ensuring high availability and production readiness.

You will design backend services, implement REST APIs, and work with Azure, Docker, Kubernetes, and CI/CD in a remote-friendly hybrid setting.

Qualifications

• 5+ years of commercial Java backend development.

Responsibilities

• Design and implement backend services in Java and Spring Boot from domain model to persistence and API layers.
• Analyze legacy Java/Spring code and Oracle PL/SQL, re-implement business logic with tests.
• Build PostgreSQL data layer, schema design, JPA/Hibernate mappings, and migrations.
• Migrate Oracle → PostgreSQL data with parallel run and safe cutover.
• Develop REST APIs (OpenAPI) and asynchronous integrations (Kafka, Azure Service Bus, RabbitMQ).
• Deliver data feeds to Databricks with data engineers.
• Write automated tests (JUnit, Testcontainers, contract tests).
• Contribute to CI/CD pipelines and containerization; deploy to Azure DEV/TEST/PROD.
• Establish logging, monitoring, and 24/7 operability; assist in production readiness.
• Collaborate with BI/PO on user stories and acceptance criteria; participate in code reviews.

Skills

Java

Spring Boot

PostgreSQL

Oracle

Azure

Docker

Kubernetes

REST APIs

Kafka

Testcontainers

CI/CD

OpenAPI

Tools

JUnit

Hibernate

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.

What you'll need to succeed in this role:

• At least 5+ years of commercial experience as a Java backend developer, with hands-on coding as your main activity in recent projects.

• Strong programming skills in Java (5+), Spring Boot, and the Spring ecosystem (Spring Data, Spring Security, Spring Integration a plus).

• Solid relational database skills: PostgreSQL and Oracle, including SQL, JPA/Hibernate, schema migrations, and performance tuning; ability to read and understand PL/SQL.

• Experience working with legacy codebases — reading, refactoring, and migrating existing logic safely.

• Experience building REST APIs and asynchronous, message-driven integrations (Kafka, Azure Service Bus, RabbitMQ, or IBM MQ).

• Working knowledge of Azure (e.g. AKS or App Service, Azure Functions, Service Bus, Key Vault, Entra ID) and containerization with Docker / Kubernetes.

• Strong testing discipline: unit, integration, and contract testing as a standard part of delivery.

• Experience with business-critical, high-availability systems where reliability and correctness matter.

• Experience using AI coding assistants / agentic workflows as part of day-to-day delivery.

• Good communication skills in English and a pragmatic, get-it-built attitude.

Discover our perks & benefits:

• Work in a supportive team of passionate enthusiasts of AI & Big Data.

• Engage with top-tier global enterprises and cutting-edge startups on international projects.

• Enjoy flexible work arrangements, allowing you to work remotely or from modern offices and coworking spaces.

• Accelerate your professional growth through career development paths, knowledge-sharing initiatives, language classes, and sponsored training and conferences. Benefit from partnerships with Databricks and Anthropic, which provide access to industry-leading training materials and certification programs.

• Participate in team-building events and utilize the integration budget.

• Celebrate work anniversaries, birthdays, and milestones.

• Access medical and sports packages, eye care, and well-being support services, including psychotherapy and coaching.

• Get full work equipment for optimal productivity, including a laptop and other necessary devices.

• With our backing, you can boost your personal brand by speaking at conferences, writing for our blog, or participating in meetups.

• Experience a smooth onboarding with a dedicated buddy, and start your journey in our friendly, supportive, and autonomous culture.