Java Engineer - Finance

Flix; Warszawa; On-site; PLN 123,000 - 164,000; Full time

Job summary

Flix is seeking a skilled Java Engineer for a freelance/B2B engagement to design and maintain Java backend features across the finance tech stack, including revenue accounting, invoicing, and settlements.

You will build and operate event-driven data pipelines with Kafka, run services on AWS, and manage CI/CD pipelines with Docker/Kubernetes. Fluent English required; open to Poland-based contractors.

Qualifications

• 3+ years of experience as a Software Engineer.
• Proven Java experience in a commercial environment.
• Experience with Kafka and cloud infrastructure (AWS).
• Solid SQL knowledge.

Responsibilities

• Design, build, and maintain backend features for internal finance apps.
• Support revenue accounting, invoicing, and bus partner settlements.
• Collaborate with finance, billing, and partner teams to shape solutions.
• Participate in product development from design to delivery and operations.
• Implement event-driven data processing workflows using Kafka.
• Contribute to CI/CD pipelines on AWS and run services with Docker/Kubernetes.

Skills

Java

Kafka

AWS

SQL

Docker

Kubernetes

CI/CD

Event‑driven

Tools

Datadog

Job description

Rate: 89 – 119 / hour (B2B)

We are looking for a skilled Java Engineer to join Flix on a freelance/service agreement basis (B2B contract). This is a contractor engagement to work on impactful, hands‑on challenges in the domain of financial technology.

Scope of Services

Bring expertise in Java‑based backend development. Work across Flix’s finance technology environment to build and maintain critical internal applications — from revenue accounting, invoices processing to bus partner settlements and payment reconciliation.

About the Engagement

• Design, build, and maintain features for the internal data‑heavy applications, supporting automated bus partner settlement generation across all FlixBus entities around the globe.
• Develop and enhance the internal services that allow finance and billing teams to manage bus partners’ settlement‑relevant data and track changes via event history.
• Communicate directly with business counterparts (finance, billing, and partner teams) to understand needs and shape solutions.
• Actively participate in product development, from refinement and technical design through delivery and operations.
• Implement and maintain event‑driven data processing workflows using Kafka to support settlement operations.
• Contribute to infrastructure‑as‑code practices and CI/CD pipelines on AWS, and run services on Docker/Kubernetes, with monitoring and observability (e.g. Datadog).

About You

• At least 3 years of experience as a Software Engineer, with exposure to data processing systems
• Proven experience working with Java in a commercial environment
• Experience with event-driven architectures, ideally Kafka
• Experience working with cloud-based infrastructure providers, ideally AWS
• Solid SQL knowledge
• Hands‑on experience with Docker and Kubernetes (or similar container orchestration tools) and CI/CD
• Familiarity with Snowflake or similar data warehousing solutions is a plus
• Experience in front‑end technologies (e.g., JavaScript, HTML5, React.js, or Angular) is a plus
• Fluent in English

Cooperation model

• Cooperation based on a service agreement (B2B/freelance contract), not an employment contract.
• You will operate as an independent contractor, responsible for delivering agreed services and submitting invoices
• Location: open for contractors based in Poland