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June 24, 2026
Senior Backend Engineer (Java, Kafka Streams, AWS)
Senior • Hybrid
30,000 - 35,000 PLN/hr
Krakow, MA, Poland
Contract: B2B or UoP
B2B budget: up to 210 PLN/h + VAT
Work model: around 3 days per week from the office
We are looking for a Senior or Staff Backend Engineer to join a small, high-impact engineering team building a large-scale, event-driven platform. This is a hands-on role for someone who enjoys working close to real production systems: high-volume data flows, asynchronous processing, external integrations, reliability, observability and technical ownership.
You will join a team where the codebase and domain are evolving, making it a strong fit for an engineer who can operate without fully predefined problems. You will be expected to investigate, create structure, improve standards and make pragmatic technical decisions.
What you will do
- Build and evolve backend services using Java and Spring Boot
- Design and maintain real-time event-processing flows using Kafka Streams
- Work with stream-processing concepts such as topologies, transformations, joins, aggregations, stateful processing and data routing
- Integrate external systems and infrastructure into a scalable internal platform
- Improve reliability, observability and production readiness of services handling high-volume data
- Investigate production issues, performance bottlenecks and data-flow problems
- Work with AWS, Kubernetes, PostgreSQL, MongoDB, Redis, Terraform and Helm
- Contribute to code reviews, architecture decisions, documentation and engineering standards
- Collaborate with product, platform and engineering stakeholders across an international environment
What we are looking for
- 7+ years of backend engineering experience
- Strong, current hands-on experience with Java and Spring Boot
- Deep practical experience with Kafka Streams in production (including stream-processing logic, joins, aggregations, windowing, state stores or topology design)
- Background in event-driven, distributed or real-time systems
- Hands-on AWS experience (EKS, S3, SQS, SNS, Kinesis or Lambda)
- Experience with Kubernetes, containers and production deployment environments
- Good understanding of PostgreSQL, MongoDB and Redis
- Strong production mindset: monitoring, debugging, reliability, performance and incident investigation
- Ability to work independently in an evolving and not always fully documented technical environment
- Clear English communication skills and confidence explaining technical topics to engineers and non-technical stakeholders
Nice to have
- Kotlin experience
- Experience with high-throughput data processing or streaming platforms
- Experience with Terraform, Helm, Prometheus, Grafana, Micrometer or similar observability tooling
- Experience in a small product team, scale-up or ownership-heavy engineering environment
- Familiarity with AI-assisted development tools
What you can expect
- A technically challenging role focused on real production systems rather than isolated feature delivery
- Strong ownership
- Small team setup with room to influence architecture, standards and ways of working
- International engineering environment
- Clear recruitment process focused on practical engineering discussions
Recruitment process
- Introductory conversation with the Hiring Manager
- Technical interview focused on Kafka use cases and Java code quality
- Final discussion with senior technical leadership
The full company and product context will be shared during the first recruiter call.
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Warsaw, Poland
120 - 150 PLN/hr
🏢 Summary: Long-term remote contract for a Senior Java Backend Engineer to design and develop a central data platform integrating transport systems using event-driven architecture and real-time stream processing. The role focuses on building scalable backend services, system integrations, and data streaming solutions in a cloud-based environment. Strong involvement in architectural decisions and high-quality code delivery is expected. 🗂️ Requirements: Minimum 6 years of experience in Java software development, Strong knowledge of Java, Commercial experience with Spring or Quarkus, Hands-on experience with Apache Kafka and Confluent, Experience with Event-Driven Architecture, Experience with Apache Flink and stream processing, Knowledge of Kafka Connect, Schema Registry and Avro, Experience with AWS services: Lambda, DocumentDB, S3, Ability to design scalable and high-performance integrations 📃 Skills: Java, Spring, Quarkus, Kafka, Confluent, Flink, AWS, Lambda, DocumentDB, S3, Avro, SchemaRegistry, KafkaConnect, REST, GraphQL 🏢 Description: Be in IT to firma rekrutacyjna, wyspecjalizowana w poszukiwaniu Specjalistów z branży technologii informatycznych. Obecnie, dla naszego klienta, poszukujemy osoby na stanowisko Senior Java Backend Engineer . Zakres obowiązków: Długofalowa współpraca z międzynarodową, topową firmą consultingową, świadczącą usługi IT dla dużych i średnich firm z różnorodnych sektorów jak automotive, finanse, bankowość czy produkcja. Praca przy rozwoju platformy pełniącej rolę centralnego źródła danych o przesyłkach, integrującej informacje z wielu systemów transportowych oraz różnych środków transportu. Projektowanie, rozwój, wdrażanie i utrzymanie rozwiązań opartych o architekturę event-driven oraz przetwarzanie danych w czasie rzeczywistym. Implementacja nowych funkcjonalności zgodnie z wymaganiami biznesowymi oraz realizacja zadań wynikających z planowanych sprintów. Rozwój i utrzymanie usług opartych o Java, Spring Framework oraz Quarkus. Budowa i rozwój rozwiązań wykorzystujących Apache Kafka, Confluent Platform oraz Apache Flink do przetwarzania strumieni danych. Projektowanie i rozwój integracji systemowych, API REST, GraphQL oraz rozwiązań analitycznych opartych o Snowflake. Praca z usługami chmurowymi AWS, w szczególności Lambda, DocumentDB, S3 oraz komponentami wspierającymi architekturę danych. Dbanie o wysoką jakość kodu, pokrycie testami, refaktoryzację oraz optymalizację wydajności rozwijanych rozwiązań. Proponowanie usprawnień architektonicznych oraz aktywny udział w podejmowaniu decyzji technicznych. Ścisła współpraca z interesariuszami technicznymi i biznesowymi oraz duża samodzielność w realizacji powierzonych zadań. Oczekujemy: Minimum 6 lat doświadczenia zawodowego w obszarze rozwoju oprogramowania z wykorzystaniem Java . Bardzo dobra znajomość Java oraz doświadczenie w pracy z Spring Framework i/lub Quarkus . Praktyczne doświadczenie z Apache Kafka , Confluent Platform oraz rozwiązaniami opartymi o Event-Driven Architecture. Doświadczenie w budowie i utrzymaniu aplikacji wykorzystujących Apache Flink oraz przetwarzanie strumieni danych. Znajomość zagadnień związanych z Kafka Connect, Schema Registry, Avro oraz zarządzaniem topicami i grupami konsumentów. Doświadczenie w pracy z usługami AWS , takimi jak Lambda, DocumentDB czy S3. Umiejętność projektowania skalowalnych i wydajnych rozwiązań integracyjnych. Mile widziane: doświadczenie z Terraform oraz znajomość Snowflake. Mile widziane: doświadczenie z BDD/Cucumber. Mile widziane: znajomość AsyncAPI oraz zagadnień związanych z asynchroniczną komunikacją pomiędzy systemami. Znajomość języka angielskiego na poziomie B2 lub C1 – umożliwiająca swobodną komunikację w międzynarodowym środowisku. Mile widziana dostępność ASAP; akceptowalny jest maksymalnie miesięczny okres wypowiedzenia ze skutkiem na koniec miesiąca. Oferujemy: Długofalowa współpraca z wynagrodzeniem w przedziale 120 - 150 PLN netto/godz. + VAT. Wsparcie przy zakładaniu i prowadzeniu działalności gospodarczej, dla osób bez takiego doświadczenia. Sprawny proces rekrutacyjny - dwie rozmowy techniczne z managerami, online (każda maksymalnie po godzinie). Współpraca w pełni zdalna na terenie Polski. Benefity - prywatna opieka medyczna, karta Multisport. Nowoczesny sprzęt zapewniany przez firmę, wraz z softem i konfiguracją.