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Addendum

Senior Software Developer (Java / Kotlin)

Addendum Vilnius, Vilnius County, Lithuania · €55K–€68K/yr

IT Services and IT Consulting · 51-200 employees

5 d ago
kotlin Senior (5-10 yrs) Full-time Lithuania
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About the role

Design, develop, test, and document secure, scalable backend functionality and automation enhancements for a securities trading project, using Java or Kotlin, Spring Boot, REST APIs, and relational databases. Build system integrations, make technical and architectural decisions, own project deliverables, and collaborate with stakeholders and technology teams to deliver high-quality solutions.

What they look for

Java Kotlin Spring Boot REST APIs Backend Development Relational Databases Data Modelling SQL Query Optimisation System Integration API Design Software Architecture Code Reviews Technical Documentation Angular Securities Trading

Requirements

Requires extensive senior-level backend development experience delivering complex or business-critical systems, with strong expertise in Java or Kotlin, Spring Boot, API development, relational databases, SQL, and system integration. Candidates must be able to independently translate business requirements into secure, maintainable solutions, manage deliverables, and communicate effectively in English; frontend or financial markets experience is an advantage.

Benefits

Personalized Benefits Packages International Team Collaboration Diverse and Challenging Projects Team Events Learning and Development Opportunities Celebration Events

Full description

ABOUT THE COMPANY:

Join ADDENDUM, a global software development and IT team augmentation firm focusing on fintech, banking, and telco industries. Experience tailored benefits, diverse projects with various tech stacks, and opportunities for growth, freedom, and responsibility you desire.

ABOUT THE ROLE:

Join a team of experienced IT professionals working on an exciting securities trading project in the banking sector, with a focus on trading automation, system integrations, and backend development. As a Senior Software Developer, you will play a key role in designing and delivering secure, scalable backend solutions and automation enhancements that reduce manual processing, improve operational efficiency, and support faster securities settlement.

Location: Vilnius, Lithuania. Candidates must be based in Vilnius, as a hybrid working model applies to this position.

Start date: From 16 November 2026 (earliest possible start).

WHAT YOU WILL BE DOING:

  • Design, develop, test, and document backend functionality for the Trading Automation project.
  • Develop secure, scalable, and maintainable solutions using Java or Kotlin, Spring Boot, and REST APIs.
  • Build and enhance system integrations within an existing application landscape.
  • Work with relational databases, including data modelling, SQL development, and query optimisation.
  • Translate business requirements into technical solutions, making well-founded architectural and design decisions.
  • Take ownership of agreed project deliverables, ensuring high-quality implementation within defined timelines.
  • Collaborate closely with business stakeholders, developers, architects, and other technology teams.
  • Participate in code reviews, testing, and technical documentation to maintain high software engineering standards.

WHAT WE EXPECT:

  • Extensive professional experience in backend software development, with a proven track record of delivering complex, integrated, or business-critical systems at a senior level.
  • Strong expertise in Java or Kotlin, Spring Boot, and API design and development.
  • Solid experience with relational databases, including data modelling, SQL, and query optimisation.
  • Proven ability to independently translate business requirements into secure, scalable, and maintainable technical solutions.
  • Hands-on experience developing system integrations and implementing changes within existing enterprise applications.
  • Strong understanding of software engineering best practices, clean code principles, code reviews, and technical documentation.
  • Ability to independently manage assigned deliverables, make technical decisions, and take responsibility for the quality of solutions.
  • Excellent communication skills in English.

Nice to have:

  • Experience with Angular or other frontend technologies.
  • Previous experience in securities trading, investment services, banking, or financial markets.
  • Familiarity with securities settlement processes and trading automation.

WHAT WE OFFER:

Salary ranges (for employees in Lithuania only): 4600 - 5700 € gross (the given range is flexible and depends on your experience).

At Addendum we believe in personalized benefits packages that cater to your unique passions. Tell us what drives you, and we'll craft a package accordingly. On top of that, here's what's in store automatically:

•

Top Talent Collaboration: Join award-winning teams from different countries.

  • Diverse, Challenging Projects: Break free from the ordinary with dynamic, stimulating work.
  • Epic Team Events: Join us for summer and winter parties and online events.
  • Learning & Development Opportunities: That new tech certificate is just around the corner.
  • Special Celebrations: We love a good shindig for birthdays and project milestones.

So, get your dancing shoes on and come join the fun!

At ADDENDUM, we wholeheartedly reject all forms of discrimination, including but not limited to age, disability, sex, sexual orientation, pregnancy and maternity, race or ethnicity, religion or belief, gender identity, marriage, civil partnership, or any other protected category. We are committed to fostering a culture of equality and inclusion, where every individual has the opportunity to thrive.

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