Java Developer (Freelancer) (m/f/d)

Freelance Mid-Level Java Developer

Location: Remote

Start Date: As soon as possible

Duration: busget is approved for 5 months with a plan of extension for a year

About the Project

We’re embarking on a high-impact backend initiative split into two major components:

1. Payment Service Provider (PSP) Migration – Transitioning from our current payment provider to a new one, including architectural redesigns to support the updated payment flow.
2. Customer Support Tool Implementation – Building a custom support tool from the ground up to handle payment-related queries, as the new provider does not offer integrated support services.

This is a unique opportunity to contribute to a widely used digital platform that supports millions of users monthly and promotes sustainable consumer behavior through secondhand trading.

Your Role

As a Mid-Level Java Developer, you’ll play a key role in both backend projects. You’ll collaborate with cross-functional teams to ensure seamless integration, robust architecture, and a smooth user experience for both internal and external stakeholders.

Responsibilities

PSP Migration

• Remove the existing payment provider and integrate a new one.
• Redesign backend architecture to support the new payment flow with scalability and security in mind.
• Coordinate with stakeholders to ensure a smooth transition of all payment-related services.

Customer Support Tool

• Build a custom support tool from scratch, integrated with the new payment system.
• Develop features for customer interaction, issue tracking, and resolution.
• Work closely with product teams to align the tool with business needs and usability standards.

General

• Write clean, maintainable, and testable code.
• Participate in regular team reviews and planning sessions.
• Ensure timely delivery of project milestones.

Your Skill Profile

• Solid experience with Java and the Spring Framework.
• Familiarity with PSP integrations and secure payment architectures.
• Strong understanding of microservices and object-oriented design.
• Experience with RDBMS and/or NoSQL databases (e.g., Cassandra, MySQL, PostgreSQL).
• Proficiency in RESTful API development.
• Experience with Continuous Delivery and test automation tools (JUnit, Testcontainers, REST-assured).
• Background in building tools or custom integrations, ideally in payments or customer support.
• Strong problem-solving skills and ability to work independently.

Please reach out to [email protected] if you have any questions.