Senior Backend Engineer (Java/Kotlin)

Quick Facts

• Role: Senior Backend Engineer (Java/Kotlin)

• Domain: Banking & Investment Technology; high-volume financial systems

Description

Build backend services for banks, investment firms, and other financial institutions, working on business-critical systems such as investment-banking platforms, transaction-processing, risk/positions, market-data, and core banking components. You’ll develop Java and/or Kotlin microservices and APIs, including event-driven, distributed, high-throughput data/transaction processing systems with strong consistency, resilience, and auditability. The work emphasizes production ownership, scalability, high availability, and observability.

Responsibilities

• Develop backend services using Java and/or Kotlin

• Build Spring Boot-based microservices and APIs

• Implement event-driven and distributed system capabilities

• Deliver high-volume transactional and data-processing services

• Create integration layers connecting internal and external financial systems

• Design for consistency, resilience, and auditability

• Build production-ready systems for scale, high availability, and observability

• Collaborate with senior engineers, architects, and business stakeholders on technical solutions

Requirements

• 5+ years of backend engineering experience

• Strong Java and/or Kotlin

• Spring Boot and microservice architecture experience

• Kafka or another event-streaming/messaging platform

• REST APIs and system integration experience

• SQL/PostgreSQL or another relational database experience

• Docker and CI/CD experience

• Experience with production systems and incident/failure handling

• Good English

• Ability to work independently and take technical ownership

Benefits

• Remote or hybrid work depending on the project

• Work in international B2B engineering environments using English on most projects

• Opportunity to work with experienced technical leadership

• AI-assisted engineering workflows to support quality, requirements context, and knowledge transfer

• B2B rate: 170–220 PLN/h + VAT (final rate depends on seniority, domain experience, and project scope)