Senior Java Developer

Leipzig

Full-time

Permanent employee

Introduction

About us

At Optimax Energy, we have been developing smart solutions for automated trading systems and promoting the transition to green energy for over 10 years. This makes us a leader in international electricity trading.

Our culturally diverse team shares a common vision and fosters a culture of appreciation and equal opportunities. We believe that we can achieve extraordinary things if we develop freely. That's why we place great value on a healthy work-life balance and encourage creative freedom.

We embrace diversity, equality and inclusion. Different perspectives and backgroundds strengthen our team and lead to creative solutions. To achieve this, we create an appreciative working environment that recognizes the uniqueness of all employees and retains talent in the long term.

In order to actively shape the future of the energy sector, we are looking for outstanding, committed individuals who share our vision and corporate culture.

Your responsibilities

Our Integrators team builds the data processing pipelines and real-time monitoring systems that power Optimax's algorithmic energy trading. We enable entry into new markets by developing integrations with national transmission system operators — your work directly determines which markets Optimax can trade in.
As Java Developer in this team, you will play a crucial role in maintaining and enhancing our existing services while driving innovation by:

Gathering and refining requirements by directly collaborating with stakeholders.
Developing new features for the trading platform.
Writing unit and integration tests, maintaining high code coverage.
Maintaining and troubleshooting services that provide essential market data for trading decisions, ensuring system reliability, scalability, and overall software quality.
Conducting code reviews and collaborating with peers to maintain high-quality standards.
Participating in workshops and encouraging knowledge sharing.
Writing technical documentation.

Status Quo

We work with the following tech stack:

Java, Spring Boot, MySQL, Clickhouse, Kafka, RabbitMQ.
Integrations: HTTP, AMQP, WebSockets, R Sockets, STOMP and email; using JSON, CSV, XML, EDI and other formats.
CI/CD: GitLab, Maven, Jenkins, TestContainers, SonarQube, Portainer and Kubernetes.
Monitoring: Micrometer, Grafana, Graylog.

Your skills

Must-Haves

At least 5 years of professional software development experience, including 3+ years in Java (senior level).
Degree in computer science or comparable field of study.
Understanding of Object-Oriented software design patterns and CLEAN code principles.
Familiarity with threads, Java Executors, concurrency models, and asynchronous programming.
Experience in implementing efficient data structures and data processing.
Familiarity with unit and integration testing.
Good communication skills in English (at least B2).
Residence in Germany and a valid work permit.

Nice-to-Haves

Experience building and managing Java projects with Maven.
Experience with Docker, Jenkins, CI/CD pipelines.
Experience designing and consuming API services.
Experience with message brokers and asynchronous messaging in general (e.g., RabbitMQ, Apache Kafka).
Knowledge of Spring Framework (Boot, Web, Messaging, Security).
Familiarity with agile methodologies (Scrum, Kanban).
Basic SQL skills for writing queries and understanding relational databases.
Performance tuning, profiling, and optimization.
Understanding of common software architecture notations and standards (UML, C4).
Background in energy markets or trading.

What we offer

How we work:
We're an office-first team as we believe in working together in person. Our Leipzig office is where ideas get picked up in the hallway, problems get solved at the whiteboard, and the occasional table tennis match happens in between. Hybrid working is part of how we operate: typically one remote day per week, but with flexibility by arrangement with your team. For this role, we're looking for someone already based in Germany with a valid work permit – relocation support isn't available at this time.

Health & well-being:

Freshly cooked lunch every day
Massages and Pilates in the office
EGYM Wellpass
Sports and mobility offers, such as subsidies for a new bike
Company health insurance that gives you access to additional healthcare services

Flexible working arrangements and benefits:

30 days paid vacation
Flexibility in working hours depending on company needs
Additional vacation for the honeymoon
Subsidies for childcare

Team culture and working atmosphere:

Regular team events (game night, table tennis tourmaments, excursions, etc.)
Work in a mission-oriented, international team that values diversity and equality
Working atmosphere with open doors and flat hierarchies
Modern, green office in the heart of Leipzig

Professional development and further training:

Independence and responsibility in project management
10% of weekly working time for personal and professional development