Senior Kotlin Microservices Lead — Fintech Platform

Sii Poland; Wrocław; On-site; PLN 180,000 - 300,000; Full time

Benefits offered by this job

Great Place to Work

Centre of internal trainings

Profit sharing

Medical care

MySii app

Regular integration events and trips

Job summary

Sii Poland is building a modern fintech platform focused on expense management and seamless integration of financial tools into partner systems such as banks, accounting platforms, and HR solutions. The team designs scalable microservices in Kotlin, emphasizing reliability and real-time control over spending.

As a Senior Backend Engineer, you will mentor engineers, drive architectural improvements, and collaborate across Platform, Services, SMB, and other domains to deliver innovative solutions

Qualifications

• Minimum 5 years of professional software development experience.
• Kotlin server-side expertise with distributed systems, microservices, and cloud environments.
• Proficiency with PostgreSQL, testing frameworks (JUnit, Testcontainers), and observability with Grafana.
• Strong problem-solving and collaborative mindset to mentor teammates.
• Very good English (B2) and residence in Poland.

Responsibilities

• Lead design, build, and maintenance of scalable microservices primarily in Kotlin.
• Collaborate with cross-functional teams across Platform, Services, SMB, and other domains.
• Analyze system performance and optimize for reliability and scale.
• Participate in code reviews, post-mortems, and mentor other engineers.
• Drive architecture improvements and guide the team through migrations and challenges.

Skills

Kotlin

Distributed systems

Microservices

AWS

Kubernetes

PostgreSQL

JUnit

Testcontainers

Grafana

English (B2)

Mentorship

Job description

Sii Poland is building a modern fintech platform focused on expense management and seamless integration of financial tools into partner systems such as banks, accounting platforms, and HR solutions. The team designs scalable microservices in Kotlin, emphasizing reliability and real-time control over spending.

As a Senior Backend Engineer, you will mentor engineers, drive architectural improvements, and collaborate across Platform, Services, SMB, and other domains to deliver innovative solutions