June 25, 2026
Senior Software Engineer
Senior • Hybrid
25,000 - 30,000 PLN
Warsaw, Poland
Join a global e-commerce technology organisation serving millions of customers across multiple international markets.
As a Senior Backend Engineer, you will become part of a team responsible for one of the company's most critical customer-facing domains. The platform supports customer subscriptions, plans, and purchasing journeys used daily by millions of users.
This is not a maintenance role. The team is actively transforming a mission-critical domain, modernising legacy systems, reducing technical debt, and building the next generation of scalable services that will support future growth.
You will play a key role in migrating core functionality from a monolithic architecture to modern microservices while helping shape the future architecture of a global platform.
What You'll Do
Build & Scale Core Services
Design, develop, and maintain scalable backend services within a distributed microservices architecture.
Build reliable systems supporting millions of customer interactions.
Improve performance, reliability, and scalability across critical customer-facing services.
Drive Modernisation
Lead the migration of key business domains from monolithic systems to modern microservices.
Reduce technical debt and improve long-term maintainability.
Design solutions that support future platform growth.
Shape Architecture
Participate in architecture discussions and technical decision-making.
Design orchestration layers supporting complex customer journeys and business processes.
Help define engineering standards and best practices.
Work with Event-Driven Systems
Build and operate services powered by event-driven architectures.
Work extensively with Kafka and real-time lifecycle events.
Design resilient and observable distributed systems.
Raise Engineering Standards
Conduct code reviews and support other engineers through technical guidance.
Promote best practices across software development, testing, deployment, and observability.
Contribute to a strong culture of ownership and continuous improvement.
AI-Powered Engineering
Use modern AI tools and coding agents throughout the software development lifecycle.
Leverage AI for onboarding, architecture exploration, implementation, testing, debugging, and productivity improvements.
Apply engineering judgement to validate, verify, and safely integrate AI-generated outputs.
What We're Looking For
Backend Engineering Expertise
5+ years of professional backend engineering experience.
Strong experience designing and operating microservices architectures.
Experience modernising legacy systems and decomposing monoliths.
Solid understanding of distributed systems and scalable backend design.
Technical Stack
Commercial experience with Go (Golang), Java, Kotlin or Scala
Engineers coming from a JVM background should be open to working in a Go-driven environment.
-
Hands-on experience with:
Kafka or similar event-streaming technologies
PostgreSQL
Docker
Kubernetes
CI/CD pipelines
Product & Ownership Mindset
Comfortable owning solutions from idea through production.
Strong problem-solving skills and ability to make technical trade-offs.
Experience collaborating with product, business, and engineering stakeholders.
AI Fluency
Practical experience using AI coding assistants such as Claude Code, Cursor, Copilot, or similar tools.
Understanding of how context, prompts, constraints, and validation influence AI-generated outputs.
Ability to critically review and verify AI-generated solutions.
Nice to Have
Experience with subscription-based products.
Experience in e-commerce environments.
GraphQL knowledge.
Familiarity with DDD, TDD, and BDD practices.
What We Offer
Opportunity to build systems used by millions of customers globally.
High-impact engineering work with significant architectural ownership.
International collaboration across distributed engineering teams.
End-to-end ownership from idea to production.
Hybrid working model (3 days per week in the Warsaw office).
B2B cooperation model.
30 days of paid annual leave.
Modern office located in Warsaw city centre.
Continuous learning and professional growth opportunities.
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Warsaw, Poland
170 - 210 PLN
🏢 Summary: Senior Backend Engineer role focused on designing and scaling a high-throughput, event-driven platform. The position centers on building and optimizing large-scale event processing services and APIs in distributed systems. It involves solving complex scalability and reliability challenges in a massive-scale environment. 🗂️ Requirements: Senior-level experience in backend development, Strong Python expertise, Experience scaling message queue systems, Experience with distributed systems and microservices architecture, Proven track record building high-throughput backend services, Experience designing scalable and fault-tolerant systems, Ability to implement and optimize APIs 📃 Skills: Python, Azure, ServiceBus, StorageQueues, EventHubs, Microservices, DistributedSystems, APIs, EventDriven, EventSourcing, Streaming, Observability, Monitoring 🏢 Description: Location: Remote Type: Full-time Level: Senior Duration: 4 months Start: ASAP We are looking for an experienced Senior Backend Engineer to join a team responsible for building and scaling a high-throughput, event-driven platform operating at massive scale. Your primary focus will be the event processing backbone — designing, developing, and optimizing services that handle large volumes of messages reliably and efficiently. You will work closely with architects and other senior engineers to implement APIs that expose data and support advanced triage and processing workflows. This role is ideal for someone who enjoys solving hard scalability problems , working with distributed systems, and building resilient backend services that operate under real-world load. Responsibilities Design and build backend services responsible for large-scale event processing Optimize and scale message-based systems to handle high throughput and reliability requirements Implement APIs defined by system architects to expose data and collect processing results Collaborate with cross-functional teams to improve platform performance and resilience Contribute to architectural decisions around scalability, fault tolerance, and observability Core Skills Strong experience with Python as a primary backend language Deep expertise in scaling message queue systems (e.g. Azure Service Bus, Storage Queues, Event Hubs or similar) Solid understanding of microservices architecture and distributed systems Proven experience building high-throughput, resilient backend services Strong problem-solving skills and ability to work with complex systems Highly Desirable Experience with event-driven or event sourcing architectures Background in data processing frameworks or streaming systems Experience building platforms related to observability, monitoring, or large-scale event management Familiarity with designing systems for fault tolerance and graceful degradation What we offer Work on technically challenging systems operating at very large scale High level of autonomy and real influence on system architecture Collaboration with experienced engineers in a mature engineering environment Competitive compensation and flexible working model Project with strong technical ownership
Technology
Reply Polska Sp. z o.o.
Senior Backend Engineer (Java, Kotlin, Spring Boot, AWS) (B2B)
Senior
Hybrid
Katowice, Poland
135 - 165 PLN
🏢 Summary: Senior backend engineering role focused on designing and scaling assortment management systems in a large retail ecosystem using Kotlin, Spring Boot, Kafka, AWS, and Kubernetes. The position involves building distributed, event-driven services, leading backend architecture evolution, and collaborating with cross-functional teams to deliver scalable enterprise solutions. The role also includes mentoring engineers, driving engineering best practices, and improving system reliability and observability. 🗂️ Requirements: Degree in Computer Science or comparable technical field, 6+ years of backend development experience, Experience with Kotlin, Experience with Spring Boot, Expertise in REST APIs, Experience with microservices, Experience with distributed systems, Experience with event-driven architectures, Hands-on experience with Kafka, Experience with asynchronous processing, Experience with AWS, Experience with Kubernetes, Experience with Amazon EKS, Experience with PostgreSQL, Experience with CI/CD, Experience with containerization, Knowledge of observability tooling, Knowledge of OAuth2, Knowledge of IAM, English proficiency, Polish proficiency, Readiness to work in hybrid model in Katowice 📃 Skills: Kotlin, Spring, SpringBoot, REST, Microservices, Kafka, AWS, Kubernetes, EKS, PostgreSQL, CI/CD, Docker, OAuth2, IAM 🏢 Description: Responsibilities We are looking for a strong backend engineer who wants to design and scale core systems powering product and assortment management across a large retail ecosystem . You will take ownership of backend architecture and system evolution within the assortment management domain , building scalable services and integrations across a complex, event-driven enterprise landscape. You act as a technical driver within the team, working closely with architects, product owners and stakeholders to deliver robust, high-quality solutions. Your key responsibilities include: Design and develop scalable backend services , APIs and integrations using Kotlin and Spring Boot within distributed systems. Translate complex business and product data requirements into robust , maintainable and scalable system designs . Lead the design and evolution of event - driven architectures and asynchronous processing using Kafka . Design and integrate backend systems within AWS and Kubernetes -based enterprise environments. Drive data modeling and persistence strategies using PostgreSQL and cloud - native approaches. Act as a technical interface between business , product and engineering teams, leading solution design and backlog refinement . Drive engineering best practices , observability , reliability and architectural consistency across the platform. Lead troubleshooting , optimization and continuous improvement initiatives while mentoring less experienced engineers. Qualifications Completed university degree in Computer Science or a comparable technical field. 6+ years of professional experience in backend development using Kotlin and Spring Boot in complex environments. Strong expertise in REST APIs , microservices , distributed systems and event - driven architectures . Deep hands-on experience with Kafka and asynchronous processing patterns in production systems. Strong experience with AWS and Kubernetes (including Amazon EKS ) in scalable environments. Solid experience with PostgreSQL and designing performant, reliable data models. Experience with CI/CD , containerization , observability tooling and modern security concepts (OAuth2, IAM). Strong communication skills in English and Polish , with readiness to work in a hybrid model in Katowice . About OBI Smart Technologies WHO ARE WE: We are a joint venture between OBI and Reply Group, responsible for co-designing, building and operating mission-critical digital platforms for commerce, customer service, and omnichannel retail. OUR MISSION: " We unite technology leadership with deep retail vision to implement standardized processes and scalable digital products that drive efficient support for one of Europe’s largest DIY retailers. Leveraging proven best practices, we advance the internationalization of products and the digital mindset of our partners, delivering consistent and business-critical solutions to support the targets of our customer. "
Technology
Inuits
Senior Backend Engineer
Senior
Hybrid
Warsaw, Poland
26,000 - 30,000 PLN
🏢 Summary: Senior Backend Engineer role focused on building and scaling backend microservices for consumer-facing platforms and internal data privacy systems. The position involves developing distributed, event-driven systems supporting personalization, search, and regulatory compliance at scale. It requires strong experience in JVM technologies and cloud-native environments. 🗂️ Requirements: Strong commercial experience with JVM-based languages (Java or Scala), Experience with Kotlin or willingness to learn, Solid understanding of microservices architecture, Experience with event-driven systems, Experience with Docker and Kubernetes, Hands-on CI/CD experience in production, Experience with unit and integration testing, Experience with relational databases and SQL, Ability to design and maintain scalable distributed systems 📃 Skills: Java, Scala, Kotlin, JVM, Microservices, Docker, Kubernetes, CI/CD, SQL, PostgreSQL, AWS, Terraform, Elasticsearch, MongoDB, GraphQL, Go, Python 🏢 Description: We are looking for a Senior Backend Engineer to join a fast-growing product organization working on consumer-facing platforms and internal data systems. This role is suited for an experienced backend engineer who is comfortable building scalable, reliable services across different domains, from customer-facing journeys to data privacy and compliance infrastructure. About the Project: You will contribute to backend systems that power core customer experiences and internal platform initiatives. Depending on the team, this includes scaling a menu and personalization platform for high-traffic consumer applications, or building a centralized Data Privacy Service handling regulatory compliance (GDPR, CCPA) and Data Subject Requests at scale. Both streams require strong engineering fundamentals, a microservices mindset, and the ability to deliver in complex, distributed environments. Responsibilities: Design, develop, and maintain scalable backend microservices across consumer or data platform domains; Build systems supporting search, personalization, customer targeting, and engagement; Develop and operate services ensuring regulatory compliance and secure data handling (GDPR, CCPA); Work with event-driven architectures and distributed systems; Contribute to CI/CD pipelines, testing practices, and overall engineering quality; Collaborate with product and engineering teams to deliver reliable and performant solutions. Qualifications: Strong commercial experience with JVM-based languages (Java, Scala, or similar); Experience with Kotlin, or willingness to learn it on the project; Solid understanding of microservices architecture and event-driven systems; Experience with Docker and Kubernetes; Hands-on CI/CD experience in a production environment; Experience with unit and integration testing; Familiarity with relational databases (e.g. PostgreSQL) and SQL; AWS and Terraform experience is a plus; Experience with Elasticsearch, MongoDB, or GraphQL is a plus; Go or Python knowledge is a nice to have; Background in e-commerce, subscription platforms, or data privacy systems is a plus. Recruitment Process: Initial interview with our recruitment team; Interview with the hiring manager; Live Coding Assessment; Meeting with the Project Manager. Inuits Sp. z o.o. is registered in the National Register of Employment Agencies (KRAZ) under number 35420.