Senior Kotlin Backend Engineer - Fintech Microservices Lead

Sii Poland; Województwo mazowieckie; On-site; PLN 250,000 - 420,000; Full time

Benefits offered by this job

Great Place to Work

Centre of internal trainings

Profit sharing

Medical care

Office environment

Job summary

Sii Poland is building a modern fintech platform that enables seamless integration of finance tools into partner systems such as banks and HR solutions. The team focuses on scalable microservices in Kotlin, cloud-native architectures, and real-time control over spending.

You will lead, design, implement, and optimize distributed systems, mentor teammates, and help drive migrations while collaborating with Platform, Services, SMB, and other domains to deliver robust solutions.

Qualifications

• Minimum 5 years of professional experience in software development.
• Expertise in server-side languages, especially Kotlin, and experience with distributed systems, microservices, and cloud environments (e.g., AWS, Kubernetes).
• Proficiency with relational databases like PostgreSQL, testing frameworks (e.g., JUnit, Testcontainers), and observability tools like Grafana.
• Strong problem-solving skills and a collaborative mindset to mentor and upskill your teammates.
• Very good knowledge of English - min. B2 level.
• Residing in Poland required.

Responsibilities

• Lead design, build, and maintenance of scalable microservices primarily using Kotlin.
• Collaborate with cross-functional teams to develop solutions across Platform, Services, SMB, and other domains.
• Analyze system performance and implement optimizations for high reliability and scalability.
• Participate in code reviews, post-mortems, and mentor other engineers.
• Improve architecture and quality of solutions and guide the team through technical challenges and migrations.

Skills

Kotlin

Distributed systems

Microservices

Cloud environments

English (B2)

Mentorship

Tools

PostgreSQL

JUnit

Testcontainers

Grafana

Kubernetes

AWS

Job description

Sii Poland is building a modern fintech platform that enables seamless integration of finance tools into partner systems such as banks and HR solutions. The team focuses on scalable microservices in Kotlin, cloud-native architectures, and real-time control over spending.

You will lead, design, implement, and optimize distributed systems, mentor teammates, and help drive migrations while collaborating with Platform, Services, SMB, and other domains to deliver robust solutions.