Senior Kotlin Engineer - Fintech Microservices & Cloud

Sii Poland; Warszawa; On-site; PLN 180,000 - 240,000; Full time

Benefits offered by this job

Great Place to Work

Solid financial situation

Contracts with the biggest brands

Centre of internal trainings

Many experts you can learn from

Open and accessible management team

Profit sharing

Passion Sponsorship program

Regular integration events and trips

Comfortable and well-equipped offices

MySii app

Medical care

Job summary

Sii Poland is seeking an experienced backend engineer to join a fintech platform developing expense management and integration with banks, accounting, and HR systems. You will design, build, and maintain scalable microservices in Kotlin, with a focus on performance and reliability.

You'll mentor teammates, participate in code reviews and migrations, and work with AWS, Kubernetes, PostgreSQL, and observability tools to continuously improve architecture.

Qualifications

• 5+ years of professional software development experience.
• Strong Kotlin server-side expertise.
• Experience with distributed systems, microservices and cloud environments.
• Proficiency with PostgreSQL and testing tools (JUnit, Testcontainers).
• Familiarity with observability tools such as Grafana.
• Excellent problem-solving and mentorship mindset.
• English at least B2.
• Residing in Poland.

Responsibilities

• Lead design, build, and maintenance of scalable microservices primarily using Kotlin.
• Collaborate with cross-functional teams 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.
• Proactively improve architecture and quality, guiding migrations and technical challenges.

Skills

Leadership

Mentoring

Collaboration

Problem-solving

English proficiency

Tools

Kotlin

PostgreSQL

JUnit

Testcontainers

Grafana

AWS

Kubernetes

Job description

Sii Poland is seeking an experienced backend engineer to join a fintech platform developing expense management and integration with banks, accounting, and HR systems. You will design, build, and maintain scalable microservices in Kotlin, with a focus on performance and reliability.

You'll mentor teammates, participate in code reviews and migrations, and work with AWS, Kubernetes, PostgreSQL, and observability tools to continuously improve architecture.