Kotlin Developer (f/m/x)

Sii Poland

Katowice

On-site

PLN 180,000 - 260,000

Full time

11 days ago

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Benefits offered by this job

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Centre of internal trainings

Profit sharing

Medical care

Job summary

Sii Poland is seeking an experienced backend engineer to join a fintech-focused team in Katowice. You will lead the design, development, and maintenance of scalable Kotlin microservices integrated with AWS/Kubernetes and PostgreSQL-backed systems.

You will mentor peers, participate in architecture reviews, and drive performance improvements for real-time financial workflows. Ideal candidates bring 5+ years of experience, strong English (B2), and a collaborative mindset to work across Platform,

Qualifications

5+ years of professional software development experience.
Expert Kotlin server-side development and distributed systems experience.
Experience with microservices and cloud environments (AWS, Kubernetes).
Proficiency with PostgreSQL, JUnit/Testcontainers, and Grafana.
Strong problem-solving and mentoring mindset.
Excellent English (minimum B2) and Polish residency.

Responsibilities

Lead design, build, and maintenance of scalable microservices in Kotlin.
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.
Drive architecture improvements and guide migrations.

Skills

Kotlin

Distributed systems

Microservices

Cloud environments

English (B2)

Mentoring

Tools

AWS

Kubernetes

PostgreSQL

JUnit

Testcontainers

Grafana

Job description

Join a team working on a modern fintech platform that supports company expense management. The project focuses on developing a finance solution that enables seamless integration of financial tools (including payment cards, expense management, and invoice handling) directly into partner systems such as banks, accounting platforms, and HR solutions. The product being developed allows companies to simplify financial processes, automate settlements, and gain full real-time control over their spending.

Your tasks

Leading initiatives to design, build, and maintain scalable microservices primarily using Kotlin
Collaborating with cross-functional teams to develop innovative solutions across Platform, Services, SMB, and other domains
Analyzing system performance and implementing optimizations to ensure high reliability and scalability
Participating in code reviews, post-mortems, and providing mentorship to other engineers
Proactively improving the architecture and quality of solutions, and leading the team through technical challenges and migrations

Requirements

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

Nice to have

Previous work in the fintech industry or with financial products
Knowledge of topics related to payments, cards, or accounting
Experience working in a scale-up environment
Proficiency in one of the following front-end technologies: React or TypeScript

Job no. JOB-EQKGG

Sii ensures that all hiring decisions are made solely on the basis of qualifications and competence. We are committed to equal and fair treatment of all, regardless of legally protected characteristics. At Sii, we promote a diverse and inclusive work environment, in full compliance with applicable anti-discrimination laws.

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