Senior Kotlin Engineer for Fintech Microservices Platform

Sii Poland; Białystok; On-site; PLN 180,000 - 280,000; Full time

Benefits offered by this job

Great Place to Work

Profit sharing

Medical care

Internal trainings

Job summary

Sii Poland in Białystok is seeking a senior backend engineer to design and maintain scalable microservices in Kotlin, focusing on a fintech platform that streamlines expense, payment, and invoice workflows.

You will collaborate with cross-functional teams across Platform, Services, SMB, and other domains, optimize performance, and lead code reviews while mentoring peers in a Polish fintech environment.

Qualifications

• 5+ years of professional software development experience
• Expertise in Kotlin and distributed systems
• Experience with microservices and cloud environments (AWS, Kubernetes)
• Relational databases (PostgreSQL) and testing/observability tools (JUnit, Testcontainers, Grafana)
• Strong problem-solving and mentorship mindset

Responsibilities

• Lead design, build, and maintenance of scalable Kotlin microservices
• Collaborate with cross-functional teams across Platform, Services, SMB, and more
• Analyze performance and implement optimizations for reliability and scalability
• Participate in code reviews, post-mortems, and mentor engineers
• Improve architecture and guide the team through technical challenges and migrations

Skills

Kotlin

Distributed systems

Microservices

AWS

Kubernetes

PostgreSQL

JUnit

Testcontainers

Grafana

English B2

Mentorship

Job description

Sii Poland in Białystok is seeking a senior backend engineer to design and maintain scalable microservices in Kotlin, focusing on a fintech platform that streamlines expense, payment, and invoice workflows.

You will collaborate with cross-functional teams across Platform, Services, SMB, and other domains, optimize performance, and lead code reviews while mentoring peers in a Polish fintech environment.