April 10, 2026
Kotlin Developer (f/m/x)
Senior • Remote
Białystok, Poland
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 requirements
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
What we offer
Great Place to Work since 2015 - it’s thanks to feedback from our workers that we get this special title and constantly implement new ideas
Employment stability - revenue of PLN 2.1BN, no debts, since 2006 on the market
We share the profit with Workers - over PLN 76M has already been allocated for this aim since 2022
Attractive benefits package - private healthcare, benefits cafeteria platform, car discounts and more
Comfortable workplace – class A offices or remote work
Dozens of fascinating projects for prestigious brands from all over the world
PLN 1 000 000 per year for your ideas - with this amount, we support the passions and voluntary actions of our workers
Investment in your growth – meetups, webinars, training platform and technology blog – you choose
Fantastic atmosphere created by all Sii Power People
If you want to work on systems with high operational significance — apply now!
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Hybrid
Łódź, Poland
🏢 Summary: Long-term backend development role in retail banking focused on building and enhancing web-based systems supporting business processes and system integrations. The position involves working with Microsoft technologies, collaborating in Scrum teams, and ensuring high code quality through automated testing and CI/CD practices. 🗂️ Requirements: Minimum 4 years of experience in backend development with C# and MS SQL, Experience with .NET 4.8/6/8, Knowledge of Entity Framework and Web API, Practical experience with CI/CD tools, Experience in unit, automated and E2E testing, Ability to work in Scrum teams, Good command of English, Availability to work from the office at least once every two weeks 📃 Skills: C#, .NET, MSSQL, EntityFramework, WebAPI, Docker, Kubernetes, Jenkins, CICD, Scrum, E2E, UnitTesting, English 🏢 Description: Dołącz do zespołu zajmującego się wsparciem procesów w obszarze bankowości detalicznej w jednym z największych banków w Polsce. Zespół tworzy systemy i narzędzia w wersji webowej, które pomagają w codziennej pracy pracowników ekosystemu, automatyzują procesy czy stanowią źródło integracji dla pozostałych systemów bankowych. Jeżeli szukasz stabilnego i długoterminowego projektu oraz chcesz rozwijać swoje umiejętności programistyczne i mieć wpływ na kształtowanie rozwoju produktu, nie zwlekaj i już dziś wyślij swoją aplikację. Twoje zadania Prowadzenie prac projektowych i implementacyjnych w systemach informatycznych opartych o technologie Microsoft Współpraca z użytkownikami biznesowymi (przy zbieraniu i analizie wymagań nowych rozwiązań) oraz z innymi zespołami IT ( m.in . DevOps, QA) Aktywny udział w działaniach zespołu Scrum Dbałość o wysoką jakość kodu poprzez tworzenie testów automatycznych, jednostkowych oraz E2E Tworzenie i aktualizacja dokumentacji technicznej Wymagania Minimum 4 lata doświadczenia przy tworzeniu i rozwijaniu modułów back-endowych w C# z MS SQL Znajomość .NET 4.8/6/8 Entity Framework, Web API Praktyczne doświadczenie z narzędziami CI/CD ( m.in . Docker, Kubernetes, Jenkins) Doświadczenie w pisaniu testów jednostkowych, automatycznych, E2E Dobra znajomość języka angielskiego Gotowość do pracy z biura min. raz na dwa tygodnie Benefity, które czekają na Ciebie: Tytuł Great Place to Work od 2015 roku - to dzięki opiniom pracowników otrzymujemy tytuł i wdrażamy nowe pomysły Stabilność zatrudnienia - 2,1 MLD PLN przychodu, brak długów, od 2006 roku na rynku Dzielimy się zyskiem z pracownikami - od 2022 roku przeznaczyliśmy na ten cel już ponad 76 milionów PLN Bogaty pakiet benefitów - prywatna opieka zdrowotna, platforma kafeteryjna, zniżki na samochody i więcej Komfortowe miejsce pracy - pracuj w naszych biurach klasy A lub zdalnie Dziesiątki fascynujących projektów dla prestiżowych marek z całego świata 1 000 000 PLN rocznie na Twoje pomysły - taką kwotą wspieramy pasje i akcje wolontariackie naszych pracowników Stawiamy na Twój rozwój - meetupy, webinary, platforma szkoleniowa i blog technologiczny – Ty wybierasz Fantastyczna atmosfera stworzona przez wszystkich Sii Power People Dołącz do zespołu Sii – rozwijaj umiejętności, zdobywaj doświadczenie i buduj karierę!
Technology
Sii
.NET Developer (f/m/x)
Senior
Hybrid
Gdansk, PM, Poland
🏢 Summary: Backend Developer role focused on building and developing web-based systems supporting retail banking processes using Microsoft technologies. The position involves designing and implementing backend modules, ensuring code quality through automated testing, and collaborating within a Scrum team. It offers a long-term project with impact on product development and system integration. 🗂️ Requirements: Minimum 4 years of experience in backend development with C# and MSSQL, Experience with .NET 4.8/6/8, Knowledge of Entity Framework, Experience with WebAPI, Practical experience with CI/CD tools (Docker, Kubernetes, Jenkins), Experience in writing unit, automated, and E2E tests 📃 Skills: C#, MSSQL, .NET, EntityFramework, WebAPI, Docker, Kubernetes, Jenkins, CICD, UnitTesting, E2E 🏢 Description: Dołącz do zespołu zajmującego się wsparciem procesów w obszarze bankowości detalicznej w jednym z największych banków w Polsce. Zespół tworzy systemy i narzędzia w wersji webowej, które pomagają w codziennej pracy pracowników ekosystemu, automatyzują procesy czy stanowią źródło integracji dla pozostałych systemów bankowych. Jeżeli szukasz stabilnego i długoterminowego projektu oraz chcesz rozwijać swoje umiejętności programistyczne i mieć wpływ na kształtowanie rozwoju produktu, nie zwlekaj i już dziś wyślij swoją aplikację. Twoje zadania Prowadzenie prac projektowych i implementacyjnych w systemach informatycznych opartych o technologie Microsoft Współpraca z użytkownikami biznesowymi (przy zbieraniu i analizie wymagań nowych rozwiązań) oraz z innymi zespołami IT ( m.in . DevOps, QA) Aktywny udział w działaniach zespołu Scrum Dbałość o wysoką jakość kodu poprzez tworzenie testów automatycznych, jednostkowych oraz E2E Tworzenie i aktualizacja dokumentacji technicznej Wymagania Minimum 4 lata doświadczenia przy tworzeniu i rozwijaniu modułów back-endowych w C# z MS SQL Znajomość .NET 4.8/6/8 Entity Framework, Web API Praktyczne doświadczenie z narzędziami CI/CD ( m.in . Docker, Kubernetes, Jenkins) Doświadczenie w pisaniu testów jednostkowych, automatycznych, E2E Dobra znajomość języka angielskiego Gotowość do pracy z biura min. raz na dwa tygodnie Benefity, które czekają na Ciebie: Tytuł Great Place to Work od 2015 roku - to dzięki opiniom pracowników otrzymujemy tytuł i wdrażamy nowe pomysły Stabilność zatrudnienia - 2,1 MLD PLN przychodu, brak długów, od 2006 roku na rynku Dzielimy się zyskiem z pracownikami - od 2022 roku przeznaczyliśmy na ten cel już ponad 76 milionów PLN Bogaty pakiet benefitów - prywatna opieka zdrowotna, platforma kafeteryjna, zniżki na samochody i więcej Komfortowe miejsce pracy - pracuj w naszych biurach klasy A lub zdalnie Dziesiątki fascynujących projektów dla prestiżowych marek z całego świata 1 000 000 PLN rocznie na Twoje pomysły - taką kwotą wspieramy pasje i akcje wolontariackie naszych pracowników Stawiamy na Twój rozwój - meetupy, webinary, platforma szkoleniowa i blog technologiczny – Ty wybierasz Fantastyczna atmosfera stworzona przez wszystkich Sii Power People Dołącz do zespołu Sii – rozwijaj umiejętności, zdobywaj doświadczenie i buduj karierę!
Technology
Sii
Senior Frontend Developer with AWS (f/m/x)
Senior
On-site
Warsaw, Poland
🏢 Summary: Senior Software Engineer role focused on building scalable front-end and cloud-native applications, with flexibility for deep specialization in modern front-end technologies or AWS cloud engineering. The position involves designing serverless architectures, integrating APIs, managing databases, and implementing CI/CD pipelines in a collaborative environment. Regular on-site presence and strong English communication skills are required. 🗂️ Requirements: Minimum 8 years of commercial software development experience, Strong expertise in front-end development with component-based frameworks or AWS cloud engineering, Hands-on experience designing and delivering cloud-native applications, Experience with serverless architectures, Solid understanding of API design principles and distributed systems, Experience with CI/CD pipelines and deployment automation, Ability to communicate fluently in English, Availability for regular on-site work 📃 Skills: JavaScript, TypeScript, AWS, Serverless, REST, SQL, NoSQL, CI/CD, Docker, Kubernetes 🏢 Description: We are looking for a highly experienced Software Engineer with strong expertise in modern front-end technologies and cloud-based solutions. In this role, you will be responsible for designing and delivering scalable, high-quality applications in a highly collaborative and fast-paced environment. The position requires regular on-site presence and the ability to communicate effectively in English with both technical and non-technical stakeholders. Depending on your strengths, we welcome candidates with either deep front-end specialization or strong hands-on experience in cloud engineering, ideally combining both. Your tasks Develop and maintain applications using modern front-end technologies and strongly typed languages Design and implement scalable cloud-based architectures, including serverless solutions Build and integrate RESTful services to support application functionality Work with both relational and non-relational databases to manage and process data effectively Create and optimize automated deployment pipelines for continuous integration and delivery Collaborate with stakeholders to translate business requirements into technical solutions Requirements Minimum 8 years of commercial experience in software development using modern programming languages Strong hands-on expertise in either front-end development (including component-based frameworks) or cloud engineering (AWS) Practical experience designing and delivering cloud-native applications, preferably in a serverless environment Solid understanding of API design principles and best practices for distributed systems Experience working with CI/CD pipelines and deployment automation tools Excellent communication skills with the ability to explain technical concepts clearly, and fluency in English What we offer Great Place to Work since 2015 - it’s thanks to feedback from our workers that we get this special title and constantly implement new ideas Employment stability - revenue of PLN 2.1BN, no debts, since 2006 on the market We share the profit with Workers - over PLN 76M has already been allocated for this aim since 2022 Attractive benefits package - private healthcare, benefits cafeteria platform, car discounts and more Comfortable workplace – class A offices or remote work Dozens of fascinating projects for prestigious brands from all over the world PLN 1 000 000 per year for your ideas - with this amount, we support the passions and voluntary actions of our workers Investment in your growth – meetups, webinars, training platform and technology blog – you choose Fantastic atmosphere created by all Sii Power People If you want to work on systems with high operational significance — apply now!