Senior Distributed Systems Engineer (Java)

🏢 Summary: Design and lead the implementation of highly scalable, high‑performance ad serving and tracking systems, building and optimizing HTTP/gRPC services and batch jobs in Java and Python. The role combines hands-on development with technical leadership, focusing on observability, reliability, and measurable performance improvements in distributed production environments. You will work on globally distributed systems handling large-scale traffic with strong engineering and code quality standards. 🗂️ Requirements: Experience designing and implementing high-performance, scalable distributed systems, Strong knowledge of Java and Python, Experience building and maintaining HTTP and gRPC services, Understanding of Internet protocols (DNS, HTTP, cookies), Knowledge of concurrency and distributed systems concepts, Ability to monitor, analyze and optimize production systems, Experience with high scalability and high availability architectures, Fluent English and Polish (C1) 📃 Skills: Java, Python, HTTP, gRPC, DNS, Aerospike, Memcached, GCP, BigQuery, MinIO, Kafka, Clickhouse, PostgreSQL, Elasticsearch, Kubernetes, Prometheus, Jenkins, Graphite 🏢 Description: You will: Design and lead implementation of system changes that deliver high performance, scalability and observability for displaying and tracking ads world wide. Develop tools and optimizations to drive measurable improvements in critical user performance metrics. Implement, test, deploy, monitor and maintain (in all aspects, including setting up environment, writing configuration code, monitor production) HTTP / gRPC services and batch jobs in Java and Python, ensuring adherence to the high engineering standards. Provide hands-on technical leadership: solving complex system challenges, participating in planning and scoping of projects, and ensuring the implementation of the highest coding standards through participation in code reviews. Desired experience: Excellent understanding of how complex IT systems work - from the hardware level, through software, to algorithms. Very good knowledge of fundamental Internet protocols and technologies (DNS, HTTP, cookies and others). Good knowledge of basic methods of creating concurrent programs and distributed systems (from thread level to geo-distributed clusters level). Practical ability to observe, monitor and analyse the operation of production systems (and draw valuable conclusions from it). The ability to critically analyze the solutions created in terms of performance (from estimating the theoretical performance of the designed systems to detecting and removing actual performance problems in production). General knowledge of issues (typical problems and methods of solving them) in the areas of 'high scalability' and 'high availability'. C1 level in English and Polish. Nice to have: Experience in the AdTech/Real Time Bidding space. Experience contributing to Real User Monitoring (RUM) systems. Selected technologies used: Java, Python Aerospike, Memcached Google Cloud Platform, BigQuery, MinIO Kafka, Clickhouse PostgreSQL Elasticsearch Kubernetes, Prometheus Jenkins, Graphite We Offer: Projects focused on extreme performance and high code quality – solid code reviews are our standard. Collaboration within an interdisciplinary, self-sufficient team (including DevOps, database experts, backend developers, product designers, and QA engineers). Hardware and software tailored to your preferences (e.g., MacBook, AI tool licenses). Flexible working conditions – no core hours, fully remote cooperation possible. Apply now! You don't need to tick every box to apply. If you are passionate about software engineering, send us your CV, and we'll review it.

🏢 Summary: Senior-level role focused on designing and leading high-performance, scalable frontend and full-stack solutions for global ad delivery and tracking systems. The position emphasizes web performance optimization, observability (RUM and Synthetic), and architectural excellence across performance-critical features. You will drive measurable improvements in user metrics while maintaining top coding standards and technical leadership. 🗂️ Requirements: 8+ years of hands-on software engineering experience, Strong understanding of frontend development and internal mechanisms, Proven experience in web performance optimization and advanced loading strategies, Proficiency in JavaScript and TypeScript, Experience with modern frontend frameworks (React), Experience with build tools (Webpack or Vite), Knowledge of Internet protocols and technologies (DNS, HTTP, cookies), Experience monitoring and analyzing production systems, Understanding of full-stack concepts and backend APIs (Node.js, Python, or Java), Experience with deployment and CI/CD pipelines 📃 Skills: JavaScript, TypeScript, React, Node.js, Python, Java, Webpack, Vite, DNS, HTTP, Cookies, RUM, Synthetic, CICD, Caching, Monitoring 🏢 Description: You will: Design and lead implementation of system changes that deliver high performance, scalability and observability for displaying and tracking ads world wide. Develop tools and optimizations to drive measurable improvements in critical user performance metrics. Implement and maintain high-quality frontend and full-stack solutions for displaying Ads globally, focusing on extreme performance and scalability. Develop monitoring systems (RUM and Synthetic) to track crucial metrics like reliability or viewability and use data to diagnose and resolve performance bottlenecks. Collaborate closely with Ads Layouts specialists and backend engineers to ensure smooth data flow and optimal architectural alignment for performance-critical features. Write, test, and deploy robust, efficient, and well-documented code in JavaScript/TypeScript/Python/Java, ensuring adherence to the highest coding and performance standards. Provide hands-on technical leadership: solving complex system challenges, participating in planning and scoping of projects, and ensuring the implementation of the highest coding standards through participation in code reviews. Requirements: 8+ years of hands-on experience in software engineering, including the understanding of Frontend Development and its internal mechanisms. Practical experience and strong understanding of Web Performance optimization techniques and advanced loading strategies (caching, asset delivery). Solid proficiency in JavaScript/TypeScript and modern frameworks like e.g., React. Experience with relevant build tooling (e.g., Webpack, Vite). Very good knowledge of fundamental Internet protocols and technologies (DNS, HTTP, cookies and others). Practical ability to observe, monitor and analyse the operation of production systems (and draw valuable conclusions from it). Good understanding of full-stack concepts, including working with backend APIs (Node.js, Python, or Java) and deployment/CI/CD pipelines. C1 level in English and Polish. Nice to have: Experience in the AdTech/Real Time Bidding space. Experience contributing to Real User Monitoring (RUM) systems. Selected technologies used: You will be working within a modern stack that includes JavaScript/TypeScript, React, Node.js, Python, and Java. We Offer: Projects focused on extreme performance and high code quality – solid code reviews are our standard. Collaboration within an interdisciplinary, self-sufficient team (including DevOps, database experts, backend developers, product designers, and QA engineers). Hardware and software tailored to your preferences (e.g., MacBook, AI tool licenses). Flexible working conditions – no core hours, fully remote cooperation possible. Apply now! You don't need to tick every box to apply. If you are passionate about software engineering or web performance, send us your CV, and we'll review it.

🏢 Summary: Lead the design and implementation of high-performance, scalable frontend and full-stack solutions for globally distributed ad systems, with a strong focus on web performance and observability. The role involves optimizing critical user metrics, building monitoring systems, and ensuring robust architecture and code quality across performance-sensitive features. 🗂️ Requirements: 8+ years of hands-on software engineering experience, Strong expertise in frontend development and internal browser mechanisms, Proven experience in web performance optimization and advanced loading strategies, Proficiency in JavaScript and TypeScript, Experience with modern frontend frameworks such as React, Experience with build tools such as Webpack or Vite, Solid understanding of Internet protocols including DNS and HTTP, Ability to monitor, analyze, and diagnose production system performance, Understanding of full-stack concepts and backend API integration, Experience with CI/CD pipelines 📃 Skills: JavaScript, TypeScript, React, Node.js, Python, Java, Webpack, Vite, DNS, HTTP, RUM, CICD, Caching 🏢 Description: You will: Design and lead implementation of system changes that deliver high performance, scalability and observability for displaying and tracking ads world wide. Develop tools and optimizations to drive measurable improvements in critical user performance metrics. Implement and maintain high-quality frontend and full-stack solutions for displaying Ads globally, focusing on extreme performance and scalability. Develop monitoring systems (RUM and Synthetic) to track crucial metrics like reliability or viewability and use data to diagnose and resolve performance bottlenecks. Collaborate closely with Ads Layouts specialists and backend engineers to ensure smooth data flow and optimal architectural alignment for performance-critical features. Write, test, and deploy robust, efficient, and well-documented code in JavaScript/TypeScript/Python/Java, ensuring adherence to the highest coding and performance standards. Provide hands-on technical leadership: solving complex system challenges, participating in planning and scoping of projects, and ensuring the implementation of the highest coding standards through participation in code reviews. Requirements: 8+ years of hands-on experience in software engineering, including the understanding of Frontend Development and its internal mechanisms. Practical experience and strong understanding of Web Performance optimization techniques and advanced loading strategies (caching, asset delivery). Solid proficiency in JavaScript/TypeScript and modern frameworks like e.g., React. Experience with relevant build tooling (e.g., Webpack, Vite). Very good knowledge of fundamental Internet protocols and technologies (DNS, HTTP, cookies and others). Practical ability to observe, monitor and analyse the operation of production systems (and draw valuable conclusions from it). Good understanding of full-stack concepts, including working with backend APIs (Node.js, Python, or Java) and deployment/CI/CD pipelines. C1 level in English and Polish. Nice to have: Experience in the AdTech/Real Time Bidding space. Experience contributing to Real User Monitoring (RUM) systems. Selected technologies used: You will be working within a modern stack that includes JavaScript/TypeScript, React, Node.js, Python, and Java. We Offer: Projects focused on extreme performance and high code quality – solid code reviews are our standard. Collaboration within an interdisciplinary, self-sufficient team (including DevOps, database experts, backend developers, product designers, and QA engineers). Hardware and software tailored to your preferences (e.g., MacBook, AI tool licenses). Flexible working conditions – no core hours, fully remote cooperation possible. Apply now! You don't need to tick every box to apply. If you are passionate about software engineering or web performance, send us your CV, and we'll review it.

🏢 Summary: Senior engineer role focused on designing and implementing high‑performance, scalable frontend and full‑stack solutions for global ad delivery systems. The position emphasizes web performance optimization, observability, and monitoring (RUM and Synthetic) to improve critical user metrics. You will lead technical initiatives, build performance‑critical features, and ensure high code quality across JavaScript/TypeScript-based systems. 🗂️ Requirements: 8+ years of hands-on software engineering experience, Strong understanding of frontend development and internal browser mechanisms, Practical experience with web performance optimization techniques, Proficiency in JavaScript and TypeScript, Experience with modern frontend frameworks (React), Experience with build tools (Webpack or Vite), Knowledge of Internet protocols (DNS, HTTP, cookies), Experience monitoring and analyzing production systems, Understanding of full-stack architecture and backend APIs (Node.js, Python, or Java), Experience with CI/CD pipelines 📃 Skills: JavaScript, TypeScript, React, Node.js, Python, Java, Webpack, Vite, DNS, HTTP, cookies, CI/CD, RUM, Synthetic, caching, observability, APIs 🏢 Description: You will: Design and lead implementation of system changes that deliver high performance, scalability and observability for displaying and tracking ads world wide. Develop tools and optimizations to drive measurable improvements in critical user performance metrics. Implement and maintain high-quality frontend and full-stack solutions for displaying Ads globally, focusing on extreme performance and scalability. Develop monitoring systems (RUM and Synthetic) to track crucial metrics like reliability or viewability and use data to diagnose and resolve performance bottlenecks. Collaborate closely with Ads Layouts specialists and backend engineers to ensure smooth data flow and optimal architectural alignment for performance-critical features. Write, test, and deploy robust, efficient, and well-documented code in JavaScript/TypeScript/Python/Java, ensuring adherence to the highest coding and performance standards. Provide hands-on technical leadership: solving complex system challenges, participating in planning and scoping of projects, and ensuring the implementation of the highest coding standards through participation in code reviews. Requirements: 8+ years of hands-on experience in software engineering, including the understanding of Frontend Development and its internal mechanisms. Practical experience and strong understanding of Web Performance optimization techniques and advanced loading strategies (caching, asset delivery). Solid proficiency in JavaScript/TypeScript and modern frameworks like e.g., React. Experience with relevant build tooling (e.g., Webpack, Vite). Very good knowledge of fundamental Internet protocols and technologies (DNS, HTTP, cookies and others). Practical ability to observe, monitor and analyse the operation of production systems (and draw valuable conclusions from it). Good understanding of full-stack concepts, including working with backend APIs (Node.js, Python, or Java) and deployment/CI/CD pipelines. C1 level in English and Polish. Nice to have: Experience in the AdTech/Real Time Bidding space. Experience contributing to Real User Monitoring (RUM) systems. Selected technologies used: You will be working within a modern stack that includes JavaScript/TypeScript, React, Node.js, Python, and Java. We Offer: Projects focused on extreme performance and high code quality – solid code reviews are our standard. Collaboration within an interdisciplinary, self-sufficient team (including DevOps, database experts, backend developers, product designers, and QA engineers). Hardware and software tailored to your preferences (e.g., MacBook, AI tool licenses). Flexible working conditions – no core hours, fully remote cooperation possible. Apply now! You don't need to tick every box to apply. If you are passionate about software engineering or web performance, send us your CV, and we'll review it.

🏢 Summary: The offer is for a software engineer role focused on designing and optimizing high-performance, low-latency systems handling over 24 million queries per second. The position involves building scalable and reliable distributed components, improving performance, and developing monitoring and testing tools in a production environment. The role emphasizes high availability, scalability, and working with modern cloud and data technologies. 🗂️ Requirements: Proficiency in programming, Strong understanding of complex IT systems from hardware to algorithms, Knowledge of Internet protocols (DNS, HTTP, cookies), Knowledge of concurrent programming and distributed systems, Experience with monitoring and analyzing production systems, Ability to optimize system performance and resolve performance issues, Knowledge of high scalability and high availability concepts, C1 level English, C1 level Polish 📃 Skills: Java, Python, Aerospike, Memcached, GCP, BigQuery, MinIO, Kafka, Clickhouse, PostgreSQL, Elasticsearch, Kubernetes, Prometheus, Jenkins, Graphite, DNS, HTTP 🏢 Description: You Will: Design and programming of a wide range of modules and components as part of a system that supports over 24M queries per second and low latency. Work on the optimization of the developed software in terms of response time and resource consumption Ensure the reliability and scalability of the solutions built Create performance and correctness tests for new system components Analyse new technologies in terms of their applicability in production conditions Develop tools for monitoring and analysing the operation of the production system Continuous optimization of existing tools and processes Desired Experience: Proficiency in programming Excellent understanding of how complex IT systems work (from the hardware level, through software, to algorithmics) Very good knowledge of fundamental Internet protocols and technologies (DNS, HTTP, cookies and others) Good knowledge of basic methods of creating concurrent programs and distributed systems (from thread level to continent level) Practical ability to observe, monitor and analyse the operation of production systems (and draw valuable conclusions from it) The ability to critically analyze the solutions created in terms of performance (from estimating the theoretical performance of the designed systems to detecting and removing actual performance problems in production) General knowledge of issues (typical problems and methods of solving them) in the areas of 'high scalability' and 'high availability' C1 level in English and Polish Selected Technologies: Java, Python Aerospike, Memcached Google Cloud Platform, BigQuery, MinIO Kafka, Clickhouse PostgreSQL Elasticsearch Kubernetes, Prometheus Jenkins, Graphite We Offer: Projects focused on extreme performance and high code quality – clean code and solid code reviews are our standard. Collaboration within an interdisciplinary, self-sufficient team (including DevOps, database experts, backend developers, product designers, and QA engineers). Access to modern technologies and the opportunity to apply them in large-scale, high-impact projects. Cooperation based on B2B contract. You can cooperate 100 % remotely or choose one of our office spaces in Warsaw or Cracow. Apply now! You don't need to tick every box to apply. If you are passionate about digital marketing, send us your CV, and we'll review it.

🏢 Summary: Technical leadership role focused on designing, developing, and scaling complex system-level solutions in areas such as deployment, monitoring, databases, and load balancing. The position combines hands-on programming with architectural ownership and coordination of a small engineering team. Emphasis is placed on building reliable, high-performance distributed systems within large-scale infrastructure. 🗂️ Requirements: Extensive programming experience, Experience designing complex IT systems, Ability to lead technical design and implementation, Experience leading project teams, Strong knowledge of concurrent programming, Strong knowledge of distributed systems, Performance analysis and optimization skills, Understanding of infrastructure components (deployment, monitoring, databases, load balancing), Ability to conduct code reviews, C1 English, C1 Polish 📃 Skills: Java, Python, Kubernetes, Prometheus, Aerospike, Memcached, GCP, BigQuery, MinIO, Kafka, ClickHouse, PostgreSQL, Elasticsearch, Jenkins, Graphite, Concurrency, DistributedSystems, LoadBalancing, Monitoring, Deployment 🏢 Description: If you enjoy working on technically complex and challenging solutions, have a strong interest in system-related topics such as deployment, monitoring, databases, and load balancing, and have experience leading the design and development of complex projects while coordinating the work of others, this role could be a great fit for you. You Will: Plan and then hands-on lead further development within a given technical area like deployment, monitoring, databases or load balancing, in the context of existing infrastructure within RTB House; Coordinate the work of a project team of 3-4 people, also making arrangements with other teams and units within RTB House; Ensure the reliability and scalability of the solutions built. Desired Experience: Excellent understanding of how complex IT systems work - from the hardware level, through software, to algorithms; Ability to proactively define requirements, ask appropriate questions and draw conclusions that will combine technical constraints and business needs; Ability to lead the design and implementation of a solution; Experience in leading project teams; Willingness to be involved in topics that go beyond programming and design, such as responsibility for technical areas or communication with other teams; Proactive attitude, independence in taking action; Extensive experience in programming and readiness to implement key system elements as well as involvement in code reviews; Good knowledge of methods of creating concurrent programs and distributed systems; Ability to critically analyze created solutions in terms of performance (from estimating the theoretical performance of designed systems to detecting and removing actual performance problems in production); C1 level in English and Polish. Selected technologies used: Java, Python Kubernetes, Prometheus Aerospike, Memcached Google Cloud Platform, BigQuery, MinIO Kafka, Clickhouse PostgreSQL Elasticsearch Jenkins, Graphite We Offer: Attractive compensation; Work in a team of enthusiasts who are willing to share their knowledge and experience; Flexible cooperation conditions - we do not have core hours, we do not have holiday limits; Access to the latest technologies and the possibility of real use of them in a large-scale and highly dynamic project; You can work fully remotely or in a hybrid model (we have an office in Warsaw and Cracow).

🏢 Summary: Technical leadership role within Platform Engineering focused on designing and developing scalable, reliable infrastructure components such as deployment, monitoring, databases, and load balancing. The position involves leading complex system-level projects and coordinating a small engineering team while contributing hands-on to critical system elements. The role centers on building and optimizing distributed, high-performance systems in a large-scale production environment. 🗂️ Requirements: Extensive programming experience with hands-on contribution to core system components, Strong knowledge of concurrent programming and distributed systems, Experience designing and implementing complex system architectures, Ability to analyze and optimize system performance in production environments, Experience with deployment, monitoring, databases, and load balancing, Experience leading technical projects and coordinating engineering teams, Understanding of complex IT systems from hardware to software and algorithms, Ability to define technical requirements aligned with business constraints 📃 Skills: Java, Python, Kubernetes, Prometheus, Aerospike, Memcached, GCP, BigQuery, MinIO, Kafka, Clickhouse, PostgreSQL, Elasticsearch, Jenkins, Graphite, Concurrency, DistributedSystems, LoadBalancing, Monitoring, Databases, Deployment 🏢 Description: Our Platform Engineering team, within the Bidding Platform structure, is looking for engineers with a strong interest in system-related topics (deployment, monitoring, databases, load balancing), as well as experience in leading the specification and development of complex projects and coordinating the work of others. If you want to work on technically challenging and sophisticated solutions, this is the opportunity for you! You Will: Plan and then hands-on lead further development within a given technical area like deployment, monitoring, databases or load balancing, in the context of existing infrastructure within RTB House; Coordinate the work of a project team of 3-4 people, also making arrangements with other teams and units within RTB House; Ensure the reliability and scalability of the solutions built. Desired Experience: Excellent understanding of how complex IT systems work - from the hardware level, through software, to algorithms; Ability to proactively define requirements, ask appropriate questions and draw conclusions that will combine technical constraints and business needs; Ability to lead the design and implementation of a solution; Experience in leading project teams; Willingness to be involved in topics that go beyond programming and design, such as responsibility for technical areas or communication with other teams; Proactive attitude, independence in taking action; Extensive experience in programming and readiness to implement key system elements as well as involvement in code reviews; Good knowledge of methods of creating concurrent programs and distributed systems; Ability to critically analyze created solutions in terms of performance (from estimating the theoretical performance of designed systems to detecting and removing actual performance problems in production); C1 level in English and Polish. Selected technologies used: Java, Python Kubernetes, Prometheus Aerospike, Memcached Google Cloud Platform, BigQuery, MinIO Kafka, Clickhouse PostgreSQL Elasticsearch Jenkins, Graphite We Offer: Attractive compensation; Work in a team of enthusiasts who are willing to share their knowledge and experience; Flexible cooperation conditions - we do not have core hours, we do not have holiday limits; Access to the latest technologies and the possibility of real use of them in a large-scale and highly dynamic project; You can work fully remotely or in a hybrid model (we have an office in Warsaw and Cracow).

🏢 Summary: Senior Engineer role focused on designing and leading high-performance, highly scalable components of a real-time bidding platform processing over 20 million requests per second. The position involves building, optimizing and maintaining distributed HTTP/gRPC services and batch jobs in Java and Python, while ensuring observability, reliability and top engineering standards. The role combines deep technical expertise with hands-on leadership in complex, cross-team projects. 🗂️ Requirements: Excellent understanding of complex IT systems from hardware to algorithms, Very good knowledge of Internet protocols (DNS, HTTP, cookies), Knowledge of concurrent programming and distributed systems, Ability to monitor, analyze and troubleshoot production systems, Ability to analyze and optimize system performance, Knowledge of high scalability and high availability concepts, Fluent English and Polish (C1) 📃 Skills: Java, Python, DNS, HTTP, gRPC, Aerospike, Memcached, GCP, BigQuery, MinIO, Kafka, Clickhouse, PostgreSQL, Elasticsearch, Kubernetes, Prometheus, Jenkins, Graphite 🏢 Description: RTB House is a global company that provides state-of-the-art marketing technologies for top brands and agencies worldwide. Its proprietary ad-buying engine is the first in the world to be powered entirely by Deep Learning algorithms, enabling advertisers to generate outstanding results and reach their goals at every stage of the funnel. We are looking for Senior Engineers to support our Bidding Platform organization which is the core of the RTB business, processing over 20 million requests per second to participate in real-time auctions and display advertisements to customers from 90+ countries. If you want to work on technically complex and demanding solutions, this is the opportunity for you! Our Senior Engineers are experts who combine deep technical expertise with a strong sense of ownership, and they take on Tech Lead roles in complex, cross-team projects. You will: Design and lead implementation of system changes that deliver high performance, scalability and observability for displaying and tracking ads world wide. Develop tools and optimizations to drive measurable improvements in critical user performance metrics. Implement, test, deploy, monitor and maintain (in all aspects, including setting up environment, writing configuration code, monitor production) HTTP / gRPC services and batch jobs in Java and Python, ensuring adherence to the high engineering standards. Provide hands-on technical leadership: solving complex system challenges, participating in planning and scoping of projects, and ensuring the implementation of the highest coding standards through participation in code reviews. Requirements: Excellent understanding of how complex IT systems work - from the hardware level, through software, to algorithms. Very good knowledge of fundamental Internet protocols and technologies (DNS, HTTP, cookies and others). Good knowledge of basic methods of creating concurrent programs and distributed systems (from thread level to geo-distributed clusters level). Practical ability to observe, monitor and analyse the operation of production systems (and draw valuable conclusions from it). The ability to critically analyze the solutions created in terms of performance (from estimating the theoretical performance of the designed systems to detecting and removing actual performance problems in production). General knowledge of issues (typical problems and methods of solving them) in the areas of 'high scalability' and 'high availability'. C1 level in English and Polish. Nice to have: Experience in the AdTech/Real Time Bidding space. Experience contributing to Real User Monitoring (RUM) systems. Selected technologies used: Java, Python Aerospike, Memcached Google Cloud Platform, BigQuery, MinIO Kafka, Clickhouse PostgreSQL Elasticsearch Kubernetes, Prometheus Jenkins, Graphite We Offer: Projects focused on extreme performance and high code quality – solid code reviews are our standard. Collaboration within an interdisciplinary, self-sufficient team (including DevOps, database experts, backend developers, product designers, and QA engineers). Hardware and software tailored to your preferences (e.g., MacBook, AI tool licenses). Flexible working conditions – no core hours, fully remote cooperation possible.

🏢 Summary: The offer is for a Backend Developer role focused on building and maintaining high-performance, low-latency systems for advertising and e-commerce platforms. The position involves developing scalable microservices and APIs using Kotlin and Spring Boot, working with real-time event processing, and contributing to system architecture and scalability. The role also includes production support and collaboration within cross-functional engineering teams. 🗂️ Requirements: 3+ years of professional experience in Java backend development, Very good knowledge of Kotlin, Very good knowledge of Spring Boot, Hands-on experience with microservices architecture, Practical experience with NoSQL databases, Experience with MongoDB, Experience building and maintaining backend systems and APIs, Understanding of system design and scalable architecture principles, Experience with high-performance and high-scale systems, English level B2, Polish level C1, Experience with AI-powered coding assistants, Work permit for EU and ability to work from EU region, Availability for occasional visits to Warsaw office 📃 Skills: Java, Kotlin, Spring, SpringBoot, Microservices, MongoDB, NoSQL, REST, API, AI, Claude, Copilot, Cursor 🏢 Description: 🟣 You will be: developing and maintaining backend systems for advertising and e-commerce platforms, building low-latency, high-performance services processing large volumes of data, developing scalable microservices and APIs using Kotlin and Spring Boot, working on real-time event processing and advertising targeting mechanisms, contributing to architecture design and system scalability improvements, collaborating with stakeholders and supporting engineering best practices, including code reviews and code quality standards, participating in technical readiness/on-call support for production incidents a few days per month. 🟣 Your profile: 3+ years of professional experience in Java backend development, very good knowledge of Kotlin and Spring Boot, openness to occasional visits to the Warsaw office (1–2 days per quarter), hands-on experience with microservices architecture, practical experience working with NoSQL databases, especially MongoDB, experience building and maintaining backend systems and APIs, understanding of system design and scalable architecture principles, experience working with high-performance and high-scale systems, strong analytical thinking and problem-solving skills, ability to collaborate effectively with stakeholders and engineering teams, good communication skills in English (B2) and Polish (C1), practical experience using AI-powered assistants (e.g. Claude Code, GitHub Copilot, Cursor) to improve productivity, quality, or decision-making in software delivery. immediate availability or a short notice period is preferred. Work from the European Union region and a work permit are required. 🟣 Nice to have: experience applying GenAI in a more structured way within the SDLC, including defined workflows, prompt patterns, or tool integrations embedded into daily work, interest in and familiarity with emerging AI-driven practices (e.g. agent-based workflows, automation patterns, AI-augmented development), with a willingness to explore and experiment beyond standard approaches. 🟣 Recruitment Process: CV review – HR call – Technical Interview – Client Interview – Decision 🎁 Benefits 🎁 ✍ Development: development budgets of up to 6,800 PLN, we fund certifications e.g.: AWS, Azure, access to Udemy, O'Reilly (formerly Safari Books Online) and more, events and technology conferences, technology Guilds, internal training, Xebia Upskill. 🩺 We take care of your health: private medical healthcare, multiSport card - we subsidise a MultiSport card, mental Health Support. 🤸‍♂️ We are flexible: B2B or employment contract, contract for an indefinite period.

🏢 Summary: Senior Java Backend Engineer role focused on building and optimizing a high-load ad-serving system processing over 5 million requests per second with strict latency goals. The position involves designing critical-path components, implementing architectural improvements, and enhancing performance in a real-time bidding platform. The role emphasizes scalability, low-latency optimization, and distributed systems engineering in a microservices environment. 🗂️ Requirements: 5+ years backend engineering experience, Strong Java proficiency, Experience with Spring or Spring Boot, Hands-on SQL experience, Experience with PostgreSQL or other relational databases, Knowledge of microservices architecture, Proficiency with Linux shell, Experience with Docker 📃 Skills: Java, Spring, SpringBoot, SQL, PostgreSQL, Linux, Docker, gRPC, ProtocolBuffers, Reactor, WebFlux, Kafka, Kubernetes, JFR, async-profiler, JVM, Testcontainers, ClickHouse, Aerospike, Redis, Micrometer, Prometheus, Grafana 🏢 Description: Are you eager to work with advanced technologies and build high-performance applications capable of processing over 5 million requests per second? If yes, we have an ideal opportunity for you at LoopMe. We are a team of experienced engineers developing and supporting real-time bidding platforms for global advertisers. You will work daily with talented engineers, using technologies such as Java, Spring Boot, gRPC, Project Reactor, Kafka, ClickHouse, PostgreSQL, Aerospike, and Redis. Your main focus will be on enhancing performance, optimizing cloud infrastructure, and developing innovative features across our product range. Join us in our mission to expand the limits of possibilities in the advertising industry! We are seeking a Senior Java Backend Engineer to join our Marketplace team and help develop our high-load ad-serving system, which can process more than 5 million requests per second with a 200ms response time. What you’ll be doing Designing and tuning hot-path components for the ad-serving critical path—such as throttling, rate limiting, targeting indexes, and DSP adapters. Implementing architectural changes across services — including RTB request lifecycle, deals targeting, and multi-impression-key processing. Creating gRPC APIs and Protocol Buffers schemas to facilitate cross-team integrations. Profiling and minimizing CPU usage and allocations to achieve strict p99 latency goals. Strengthening the system architecture to guarantee smooth operation during peak load times. Integrating advanced targeting algorithms into the main ad delivery process. Collaborating closely with multiple teams to provide services and data for our solutions. Core qualifications Over five years of experience in backend engineering. Solid understanding of Java and Spring / Spring Boot. Hands-on experience with SQL and familiarity with PostgreSQL or other relational databases. Strong knowledge of microservices architecture and its best practices. Proficient in Linux shell and Docker. Additional experience we’d value Concurrency in Java includes java.util.concurrent, CompletableFuture, lock-free data structures, virtual threads / Project Loom, and Reactor schedulers. gRPC and Protocol Buffers Project Reactor / Spring WebFlux Kafka Kubernetes Experience in managing high-QPS services, including profiling with JFR and async-profiler, GC tuning, and JVM internals understanding. Robust testing culture with unit tests, functional tests, and Testcontainers. Extra pluses AdTech / RTB domain expertise — OpenRTB, DSP/SSP, IVT, deals, cookie-sync, ads.txt, schain Performance engineering on critical paths — utilizing fastutil / Eclipse Collections, creating allocation-aware code, and optimizing for JIT awareness. Distributed systems experience includes rate-limiting algorithms such as token bucket, fixed and slidingwindow, as well as back-pressure, circuit breakers, sharding, and consistent hashing. Observability tools include Micrometer, Prometheus, Grafana, and structured logging. Full responsibility for managing multi-week epics across multiple teams. Experience with analytical or in-memory databases such as ClickHouse, Aerospike, Redis. Benefits Flexible working schedule with a hybrid type of work Annual performance bonus One month of workation (you can work from any part of the world for one month) Multikafeteria