Senior Java Backend Engineer

Join our client, a pioneer in digital identity and fraud prevention solutions, serving banks, fintech firms, online marketplaces, and other regulated industries globally. Their innovative products harmoniously blend biometric identity verification, document and image processing, and sophisticated fraud detection techniques, empowering clients to deliver smooth digital experiences while upholding robust security measures and compliance with regulations. The company harnesses the power of AI, machine learning, and computer vision to enhance identity verification, mobile deposit, and liveness detection solutions utilized by thousands of organizations worldwide.About the RoleWe are in search of a Senior Java Backend Engineer to become a crucial member of our cross-functional team dedicated to developing cloud-native identity and fraud prevention products on AWS. In this pivotal position, you will architect and implement scalable, high-performance backend services and APIs in Java, operating within a microservices and serverless architecture. You will engage in close collaboration with product managers, front-end engineers, researchers, and DevOps specialists to deliver production-ready features that enable real-time identity verification and extensive fraud detection.What You Will DoDesign, develop, deploy, and maintain production-ready backend APIs and microservices in Java, primarily utilizing AWS as the deployment platform.Construct scalable and resilient services leveraging serverless and containerized architectures (ECS, Lambda, API Gateway).Write clean, efficient, and testable code, emphasizing quality engineering and continuous delivery.Design and execute robust automated test suites, including unit, integration, and performance tests.Collaborate with product managers, front-end engineers, QA, and cloud operations teams to translate requirements into well-crafted features.Contribute to the development of CI/CD pipelines and advocate for DevOps best practices to ensure rapid and reliable deployments.Create and maintain both internal software and public API documentation.Participate in Agile ceremonies such as stand-ups, sprint planning, refinements, and retrospectives.Mentor and support junior team members, sharing knowledge to elevate team capabilities.

Role Overview oscilar is hiring a Senior Backend Engineer with a focus on Java. This remote position is open to candidates based in Poland. The role centers on building and maintaining backend systems that support oscilar’s products and services. What You Will Do Work closely with teams across disciplines to design, implement, and support backend applications Develop scalable, reliable backend systems using Java Contribute to the ongoing improvement of code quality and system performance Location This is a remote role available to candidates located in Poland.

About Our Team At SumUp, we provide a comprehensive Point-of-Sale (POS) solution designed to empower businesses such as cafes, shops, bars, and salons to streamline operations and foster growth. Our platform encompasses a variety of features including product catalogs, inventory management, business analytics, compliance assistance, and loyalty programs. The Fiscalization team is dedicated to ensuring compliance in countries like Italy, Sweden, Norway, Belgium, and Austria, among others. We are also pioneering the integration with third-party services for fiscalizing receipts. As a Senior Backend Engineer, you will work alongside a vibrant, cross-functional team comprising Product Managers, Designers, Engineering Managers, and fellow engineers. Your Role In this position, you will develop secure backend systems that ensure SumUp's POS products are compliant across various countries on our roadmap. You will collaborate with the Fiscalization squad to devise unique solutions tailored to the challenges in each market. We are looking for a developer who values user-centric design, precision, and seamless collaboration. You will excel in a structured communication environment and thrive in a cross-functional team. This is a B2B role based in Warsaw. Key Responsibilities Design and maintain fiscal compliance solutions to support SumUp's expansion across Italy, Sweden, Norway, Belgium, Austria, and other European markets. Develop integrations with third-party services for receipt fiscalization and regulatory reporting. Navigate SumUp's intricate POS ecosystem and familiarize yourself with fiscalization frameworks across multiple jurisdictions. Work collaboratively with team members and stakeholders distributed across 5+ cities in a hybrid working model. You Will Succeed in This Role If You Have: 5+ years of experience in backend engineering with expertise in Java and/or Kotlin. A solid understanding of system architecture, design principles, data modeling, and API development. Hands-on experience with distributed and fault-tolerant systems. Proficiency in AWS and Kubernetes. Strong knowledge of Kafka, PostgreSQL, and CQRS.

Join our dynamic development team as an experienced Backend Engineer, where you will play a crucial role in building large-scale event-driven systems. We are collaborating with a forward-thinking integrated shipping services company, known for their innovative approach to global logistics. They maintain a smart and efficient worldwide network, providing reliable shipping services that ensure stable operations for customers globally. Your primary responsibilities will include designing and constructing event-driven solutions utilizing Kafka and related technologies, with a strong emphasis on stream processing applications, data pipelines, and monitoring solutions built with the ELK stack.

Join LoopMe, the premier in-app monetization and programmatic advertising platform. With a reach of over 900 million unique monthly users and the processing of more than 200 billion ad requests, our platform offers unparalleled opportunities for mobile app developers. The Chartboost SDK is recognized as the most-integrated independent mobile ad SDK, facilitating meaningful connections between advertisers and highly engaged audiences.What We Are Looking ForWe seek an experienced backend software engineer to become an integral part of our exchange team. Your mission will be to enhance our advertising platform, designed to handle hundreds of thousands of requests per second while conducting real-time auctions to deliver optimal ads from our global partners. We empower our engineers to take ownership of this vital system, overseeing the complete lifecycle of feature development—from initial design to production deployment.Our primary system is developed in functional Scala, providing opportunities to leverage your distributed, low-latency programming skills using modern technologies like MongoDB, protocol buffers, and more. As we transition from Scala to Java in the coming years, your expertise will be invaluable in guiding this change.Your ResponsibilitiesDesign, implement, and test functionalities for our Exchange product.Assist in the migration of our advertising exchange from Scala to Java.Collaborate effectively with engineers, system architects, and Operations teams to implement enhancements and resolve issues.Engage in technical discussions, proposing innovative solutions to enhance the product and processes.Troubleshoot application, technology, and infrastructure issues.Continuously expand your technical knowledge.Demonstrate creativity and independence while collaborating to maximize efficiency and throughput.Consistently deliver high-quality work on time and enhance developer productivity across the organization.Value clean code and possess experience in writing unit tests to maintain superior code quality.Your QualificationsBachelor’s degree in Computer Science or a related field.1+ years of Scala programming experience.2+ years of Java programming experience.6+ years of overall software engineering experience.Understanding of microservices with practical implementation experience.Experience in developing high-capacity, high-traffic, high-availability systems.Familiarity with Agile development methodologies.Preferred QualificationsExperience in advertising technology.Familiarity with Python or Java.Experience with NoSQL databases.

N-iX is on the lookout for a Senior Python Engineer with proficiency in Go and Java to become a vital part of our innovative team. In collaboration with our client's team, you will contribute to the development of a state-of-the-art cloud-based security platform as a backend engineer with a robust infrastructure background. This team is dedicated to creating solutions that empower security teams to conduct forensic investigations, deploy custom scripts on a large scale, and react swiftly to cyber threats affecting millions of endpoints. The platform facilitates automated collection of forensic evidence, customizable forensic profiles, and efficient incident response workflows, all integrated within a single console alongside EDR data. Your primary focus will be on enhancing backend systems and infrastructure to enable the team to deliver high-quality solutions more efficiently.

Join our dynamic team at Renmoney as a Java Backend Developer, where you will contribute to our core engineering teams, including Banking, Loans, Core Tech Platform, and Cards. Our teams are focused on developing high-impact, backend-heavy systems that drive essential financial products and internal platforms.At Renmoney, we prioritize engineering excellence—not only in delivery speed but also in system quality and the artistry of software development. We are cultivating a collaborative engineering culture that values clear communication, thoughtful architecture, rigorous testing, and teamwork.Our tech stack includes: Java • Spring Boot • AWS (EKS) • MySQL • Kafka • Redis • Grafana • Prometheus.

Join our innovative team at dev2 as a Backend Software Engineer where you will play a crucial role in developing scalable backend solutions. Your expertise will help shape our technology stack and improve system performance. You will collaborate with cross-functional teams to design, implement, and maintain high-quality applications.

Join Turnitin as a Senior Fullstack/Backend Software Engineer, where your expertise in backend development, particularly with Java and serverless architectures, will be pivotal. We are seeking engineers who are enthusiastic about creating scalable distributed systems and delivering robust software solutions for our acclaimed educational platform.As an integral member of our shared services team, you'll spearhead the development and enhancement of the core systems supporting both our existing and upcoming applications.Key Responsibilities:Architect, develop, and optimize scalable backend services utilizing Java and serverless technologies (AWS Lambda).Design and implement RESTful APIs and event-driven architectures.Contribute to frontend component development as required.Enhance performance and cost-effectiveness of existing services.Collaborate with cross-functional teams, including Architects, Product Managers, and engineering leads, to deliver innovative solutions.Mentor junior developers and promote best practices.Establish and manage CI/CD pipelines.Maintain high-quality coding standards through peer reviews, automated testing, and compliance with development best practices.Document shared components comprehensively, providing usage guidelines and examples.

Join Netguru, a pioneering force in digital commerce, as we assist renowned brands in modernizing their B2B solutions, marketplaces, and retail ecosystems. Since our inception in 2008, we have empowered businesses through innovative technology, AI-driven personalization, and exceptional engineering and design teams. As a certified B Corporation®, we proudly serve major brands such as IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.We are currently seeking a Senior Backend Engineer with robust architectural expertise to engage in a long-term project for a European client in the laboratory and biotech sector. This position is a single-developer project, requiring close collaboration with the client’s internal teams and laboratory stakeholders to clarify requirements, outline the project scope, and enhance existing backend processes. Strong communication skills are vital, as you will frequently participate in technical discussions with LIMS and laboratory teams. Your role will encompass hands-on development, legacy code refactoring, and contributing to a scalable, well-structured backend architecture. Please note that candidates must be based in the EU due to client stipulations.Position: Senior Backend Engineer (Java / Architecture)Contract: Freelance / B2B – Remote (EU Only)Rate: 36–50 EUR/hourLanguage: English C1Key ResponsibilitiesOperate independently as the sole backend engineer on the project.Refactor and modernize legacy backend systems.Enhance and expand existing microservices and backend integrations.Maintain and develop REST and SOAP interfaces.Engage with laboratory teams and LIMS stakeholders to define requirements.Guarantee stable operation of backend services in an on-premise Kubernetes environment.Work collaboratively with internal client teams to ensure architectural consistency.QualificationsTechnical Skills & ExperienceExtensive experience with Java (Spring / Spring Boot).Strong architectural and problem-solving abilities.Proficient in designing and maintaining REST APIs.Familiarity with SOAP services.Experience in microservices environments.Hands-on experience with Kubernetes (preferably on-premise setups).Background in working with or integrating LIMS systems.Solid understanding of refactoring and modernizing legacy code.Excellent communication skills for direct collaboration with laboratory stakeholders.Proficiency in English at C1 level.Must be based in the European Union.BenefitsIn return, we offer:100% remote, flexible work environment;Access to cutting-edge technology and tools;Opportunities for professional development.

About the TeamJoin the Sell Online Tribe, a dynamic group that empowers merchants to establish their presence online. We create innovative tools that enable millions of entrepreneurs, from barbers to bakers, to market their products and services effortlessly. Our core focus lies in the Online Store and Bookings products, which form the backbone of SumUp’s ecosystem, allowing merchants to manage appointments, highlight their offerings, and process payments—all from their mobile devices.We are a collaborative, cross-functional team of Product Managers, Designers, and Engineers dedicated to delivering exceptional mobile experiences. As a part of this team, you will play a crucial role in expanding into new sectors, bridging the gap between web and mobile, and making digital selling seamless for small businesses worldwide.About the RoleAs a Senior Backend Engineer, you will be instrumental in enhancing SumUp's major merchant-facing online products within the Bifrost team. You will contribute to the development and scaling of key products such as Payment Links, Virtual Terminal, and Unified Gift Cards, while also working on integration solutions that are vital for numerous other SumUp offerings.We are looking for a developer who prioritizes reliability, teamwork, and continuous growth. Your backend expertise will thrive in a high-impact environment where your contributions directly influence merchant success and team scalability.What You’ll DoEnsure scalability and continuous growth of high-priority online products at SumUpDrive the implementation, development, and integration of Online Checkouts across SumUpEngage actively in planning and review sessions at quarterly and sprint levels, providing constructive feedback and estimationsMonitor existing services, applying necessary fixes to maintain platform reliabilityDevelop new features with maintainable and testable codeEnhance application performance for scalabilityParticipate in code reviews to uphold high coding standardsYou Will Excel in This Role If:You have 5+ years of experience in backend engineering with GolangYou possess a robust understanding of fundamental system architecture, design principles, data modeling, and API designYou have substantial experience with distributed and fault-tolerant systemsYou have a passion for delivering high-quality software solutions

Join HelloFresh in Warsaw as part of the HelloTech organization, our global technology backbone comprising over 1,000 professionals dedicated to developing digital products that enhance our comprehensive food experience. From meal kits and ready-to-eat meals to specialized offerings such as pet food and premium meat & seafood, HelloTech builds the platforms that deliver personalized food solutions to millions of customers each month. Our subscription-based, direct-to-consumer model leverages technology at every touchpoint—from customer-facing applications and personalization algorithms to pricing, forecasting, supply chain optimization, and initiatives aimed at minimizing food waste. Though our brands function independently to cater to unique customer needs, they are unified by shared platforms, data, and operational excellence fostered by HelloTech.At HelloTech, we operate in autonomous, cross-functional teams, each responsible for a specific product or domain from inception to completion. In collaboration with our Warsaw office, you will contribute to the development of scalable, data-driven products utilized across various markets, employing a modern tech stack and working alongside international teams to continually enhance how people discover, order, and enjoy HelloFresh’s offerings, both now and into the future.

Mission Statement: Kontakt.io is creating a transformative platform for care operations.Our innovative solutions minimize waste, reduce costs, and enhance revenue by optimizing throughput, asset utilization, and staff productivity. Utilizing AI, Real-Time Location Systems (RTLS), and Electronic Health Record (EHR) data, our platform empowers self-learning agents to streamline workflows, adapt in real-time, and manage all care delivery operations efficiently.Designed for easy deployment and scalability, our platform offers a comprehensive view of spaces, equipment, and personnel, thereby eliminating inefficiencies and enriching the patient experience. With a demonstrable 10X return on investment and over 20 successful use cases, Kontakt.io stands as the premier choice for enhanced and expedited care delivery operations.To thrive in this role, you must possess a fervent passion for developing high-performing and dependable applications. We seek individuals who are innovative problem solvers, eager to adopt the best tools for addressing scalability challenges.Our technology stack includes: - Backend: Kotlin, Java 15+; Spring Boot, Spring Data, Kafka, MongoDB, PostgreSQL, Docker, Kubernetes, Python, AWSWe are in search of a self-motivated individual who can approach challenges from a product perspective, propose effective solutions, and execute them successfully.

Dołącz do naszego zespołu jako Senior Backend Developer! Szukamy utalentowanej osoby, która będzie odpowiedzialna za długofalowe rozwijanie i utrzymywanie aplikacji backendowych. Twoje zadania będą obejmować optymalizację istniejących rozwiązań oraz zapewnienie zgodności z najlepszymi praktykami wytwarzania oprogramowania. Jeśli jesteś pasjonatem technologii i chcesz pracować w dynamicznym środowisku, to ta oferta jest dla Ciebie!

We are seeking a skilled and experienced Senior Java Engineer to join our dynamic team working on an innovative AI project in Europe. Our client, a leading American e-commerce giant based in California, operates one of the most renowned and successful platforms globally, connecting millions of sellers and buyers across more than 190 markets. Key Responsibilities: Design and implement a robust and scalable Kotlin framework for configuring and managing AI agents. Develop clean, maintainable, and efficient code adhering to established coding standards. Ensure optimal performance, quality, and responsiveness of the platform. Identify and resolve bottlenecks and errors promptly. Contribute to maintaining high code quality, organization, and automation. Create and update technical documentation for the framework/platform.

Join our dynamic team at inpost as a Senior Java Engineer. We are seeking an innovative and experienced software developer who is passionate about building high-quality applications. In this role, you will be responsible for designing, developing, and maintaining robust Java-based solutions while collaborating with cross-functional teams to enhance product functionality.

About Zowie:At Zowie, we are at the forefront of transforming customer interactions through AI. Our vision is to create an environment where AI Agents manage all customer communications, providing instant, tailored, and outstanding service.We believe that AI Agents are poised to drive the next significant technological evolution, and Zowie is leading this movement. Major brands such as Costco, DocMorris, Monos, Decathlon, and InPost trust our AI Agents to spearhead their customer service, managing millions of interactions every month.About the Role:As our GenAI-powered platform is already being utilized by large enterprises for mission-critical applications and achieving substantial results, we're expanding our engineering team to foster greater impact, seamless integrations, and quicker value delivery. We are looking for adaptable Senior Backend Engineers eager to engage with the latest in GenAI technology and contribute to pioneering impactful solutions.In this role, you will lay the groundwork that enables our AI Agents to operate at scale, crafting systems that prioritize reliability, performance, and adaptability. Interested in the technology you'll be developing? Explore these tutorials to familiarize yourself with our platform, or see it in action here.Key Points:1. This position is tailored for software engineers who think beyond a single technology stack. You should have a strong command of at least one of the following programming languages: Java, Scala, or Python, and be open to utilizing others when appropriate.2. We operate as an AI-native engineering organization, encouraging the use of modern AI tools in your daily tasks. Software engineering is rapidly evolving with new AI technologies, and you will be at the forefront of this shift: applying AI for design exploration, code scaffolding, test generation, and decision documentation, all while maintaining rigorous engineering standards—clear contracts, readable code, robust test suites, observability, and sustainable architectures. This is disciplined engineering at an accelerated pace.

Join HelloFresh in the vibrant city of Warsaw as part of our dynamic HelloTech organization, a global technology powerhouse comprising over 1,000 talented individuals. Together, we create innovative digital solutions that elevate the culinary experience for our customers. From meal kits and convenient ready-to-eat options to specialty items such as premium meats and pet food, HelloTech is the driving force behind our mission to deliver personalized food solutions to millions each month. Our subscription-based, direct-to-consumer model is deeply rooted in technology, ensuring excellence at every stage—from customer-facing applications and personalized experiences to robust pricing strategies, accurate forecasting, and optimized supply chains. Despite our brands catering to unique customer needs, we thrive on shared platforms, data, and operational excellence driven by HelloTech. At HelloTech, we operate through autonomous, cross-functional alliances, each responsible for specific products or domains. By collaborating within our Warsaw office, you will contribute to the development of scalable, data-driven products that enhance the way customers discover, order, and enjoy HelloFresh offerings, now and in the future.

Join HelloFresh in Warsaw as part of our HelloTech organization, a vital segment of our global technology team comprising over 1000 professionals. We are dedicated to developing digital products that enhance the end-to-end food experience, encompassing meal kits, ready-to-eat meals, and even specialty items like pet food and premium meat & seafood. Our technology platforms empower millions of customers with personalized food solutions every month.Our direct-to-consumer subscription model is fueled by cutting-edge technology that optimizes every customer interaction—from engaging applications and personalization algorithms to pricing strategies and supply chain management. Although our brands operate independently to cater to diverse customer needs, they are unified by shared platforms, data, and operational excellence crafted by HelloTech.At HelloTech, we work in autonomous, cross-functional teams that take ownership of specific products and domains. By collaborating with our Warsaw office, you will contribute to scalable, data-driven products used across various markets, leveraging a modern tech stack and working with international teams to continuously enhance how our customers discover, order, and enjoy HelloFresh products now and in the future.

Join the ARQ Team!At ARQ, we are revolutionizing the fintech landscape. Our aim is to transform global financial interactions, creating a seamless infrastructure for value transfer across borders. As we embark on this exciting journey, every new team member plays a crucial role in shaping our innovative products, company culture, and future growth. If you are passionate about tackling significant challenges and making a global impact while being part of a talented team, ARQ is the perfect place for you!Your RoleAs a Backend Engineer, you will be responsible for designing, developing, and maintaining robust backend systems that support our cutting-edge financial products. You'll work closely with a skilled team to craft solutions that promote financial inclusion and help users manage their finances more effectively.Key ResponsibilitiesFocus on developing new systems as well as enhancing existing ones.Engage in projects including building REST APIs, creating microservices, and evolving essential systems like card payments, treasury management, and cryptocurrency liquidity.Utilize Java 25 for backend development alongside a PostgreSQL database.Leverage Spring Boot to ensure quick and efficient delivery of solutions.Adopt a pragmatic approach to developing business logic, focusing on writing clean, maintainable code, and employing methodologies like TDD, DDD, and continuous integration and delivery.QualificationsA minimum of 5 years of experience in backend development with a strong command of Java.A Bachelor's degree or higher in Computer Science, Mathematics, Physics, or related engineering/science fields.A quick learner with a driven, results-oriented mindset and exceptional communication skills (fluent in English, both verbal and written).Proven experience in developing complex products utilized by millions in high-growth startup environments.