Senior Software Engineer (Java&Scala)

🏢 Summary: Backend Software Engineer role focused on building and scaling a high-traffic mobile advertising exchange that processes hundreds of thousands of real-time auction requests per second. The position involves full lifecycle development of distributed, low-latency microservices written in functional Scala and deployed to production. Engineers design, implement, test, and optimize backend systems for high availability and performance. 🗂️ Requirements: BS in Computer Science or related field, 6+ years of software engineering experience, 2+ years of Scala programming experience, Experience with Java or Python, Hands-on experience with microservices architecture, Experience building high-traffic, high-availability systems, Experience with Agile development, Ability to design, implement and test backend systems, Experience troubleshooting application and infrastructure issues, Experience writing unit tests 📃 Skills: Scala, Java, Python, Microservices, MongoDB, Bigtable, Aerospike, Kafka, PubSub, AWS, GCP, Git, Bitbucket, ProtocolBuffers, NoSQL 🏢 Description: LoopMe is the leading in-app monetization and programmatic advertising platform. We reach a mobile audience of over 900 million monthly unique users globally and process over 200 billion ad requests. The Chartboost SDK is the highest-integrated independent mobile ad SDK and through the Chartboost Exchange, Ad Network and other services, we empower mobile app developers to build businesses while connecting advertisers to highly engaged audiences. What we need: We are looking for a backend software engineer to join our exchange team and help us build the best advertising platform for mobile developers. You'll work on a system that processes hundreds of thousands of requests per second and conducts a real-time auction to find and deliver the most effective ads from our global partners. We trust our engineers to own this critical system and handle the full life cycle of feature development, from initial design all the way to shipping into production. Our system is written in functional Scala and has plenty of opportunities to flex your distributed, low-latency programming muscle, using technologies like mongoDB, protocol buffers and others. What you’ll be doing: Responsible for designing, implementing and testing the functionality of our Exchange product Work effectively with other engineers, system architects, and Operations teams to implement enhancements and issue resolutions Participate in technical discussions; come up with innovative ways to improve the product and process Troubleshoot issues with application, technologies, and infrastructure Continuously improve your technical knowledge Think creatively and work independently - collaborating with others as needed to maximize efficiency and throughput Deliver quality work on time while driving developer productivity across the organization You’re the type of engineer that appreciates clean code and has experience in writing unit tests to keep the utmost in code quality Qualifications: BS in Computer Science or related field 2+ years of Scala programming experience, along with experience in other programming languages such as java, or python. 6+ years of software engineering experience You have an understanding of microservices and hands-on experience implementing them You are experienced with software development in high-capacity, high-traffic, high-availability websites/systems You have experience working with Agile development The following experience would be a plus: Advertising technology experience Experience with Python or Java NoSQL databases (MongoDB, Bigtable, Aerospike etc) Distributed messaging services, like Kafka, PubSub Strong skills in Data Engineering Experience Managing Cloud infrastructure (AWS or GCP) Familiarity with Git and/or Bitbucket Benefits: International work environment Flexible working schedule with a hybrid working model (3 days from the office) Annual performance bonus (up to 8%) One month of workation (work from any location worldwide for one month) Multikafeteria

🏢 Summary: The offer is for a Java Backend Engineer to build and scale a high-load Data Management Platform processing billions of events daily in a real-time ad tech environment. The role focuses on developing and optimizing distributed data pipelines, microservices, and database schemas for performance and scalability. It involves working on complex backend systems supporting large-scale advertising auctions and audience targeting. 🗂️ Requirements: 2+ years of engineering experience, Proficiency in Java, Strong understanding of concurrency, Strong understanding of distributed systems, Experience with Spring Framework or similar IoC framework, Experience with JPA or other ORM framework, Strong knowledge of SQL, Experience with PostgreSQL or other modern RDBMS, Ability to work with large multi-module codebase 📃 Skills: Java, Spring, JPA, SQL, PostgreSQL, Spark, HBase, Kafka, Kubernetes, ORM, NoSQL 🏢 Description: We’re looking for a Java Backend Engineer to join LoopMe — a global AI-powered ad tech company redefining how brands connect with consumers across the open internet. In this role, you’ll help build and scale our Data Management Platform (DMP) — a massively distributed, high-throughput system processing billions of events daily , creating rich device and audience profiles, and exporting data segments to 50+ global partners and exchanges in real time. You’ll work on complex backend challenges around performance, scalability, data pipelines, and real-time processing , helping power the infrastructure behind large-scale advertising auctions and audience targeting. This is an opportunity to work on truly high-load systems , collaborate with experienced engineers, and have direct impact on a product used by some of the biggest players in the ad tech ecosystem. What you'll be doing: Developing features and optimizing performance for large-scale data pipelines (Spark jobs, HBase, Kafka) Designing and optimizing data schemas for relational and NoSQL databases Building microservice applications Core qualifications: 2+ years of engineering experience Proficiency in Java with a strong understanding of concurrency and distributed systems Experience with Spring Framework or similar IoC frameworks Experience with JPA or other ORM frameworks Strong knowledge of SQL and experience with modern RDBMS (PostgreSQL) Self-motivated, reliable, and comfortable working across a large multi-module codebase Additional experience we’d value: Experience with Apache Spark or other large-scale data processing frameworks Experience with HBase or other NoSQL/columnar stores Experience with Kubernetes Experience with Kafka Experience with AI/LLM integrations in backend services 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

🏢 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

🏢 Summary: Role focused on manual and exploratory testing of Android and iOS SDKs within a high-scale adtech platform, ensuring quality from feature definition through release. The position involves defining test strategies, executing regression and smoke tests, validating multi-device builds, and collaborating closely with developers and automation engineers. It contributes directly to quality standards across a growing mobile SDK portfolio. 🗂️ Requirements: 2+ years in QA or mobile testing, Experience testing Android applications, Experience testing iOS applications, Proficiency with TestRail or similar test management system, Proficiency with JIRA for bug tracking, Understanding of API testing concepts, Experience in Agile/Scrum environments, Experience with network traffic analysis tools 📃 Skills: Android, iOS, TestRail, JIRA, API, Agile, Scrum, Charles, BrowserStack, Maestro, Rust, JavaScript 🏢 Description: About LoopMe LoopMe is an AI company solving one of advertising's hardest problems: making brand advertising actually measurable — and making it perform. Our platform runs patented machine learning models across billions of consumer signals in real time, optimising campaigns toward outcomes like purchase intent, brand lift, and foot traffic rather than proxy metrics like clicks. The result is 2–5x better performance than industry benchmarks, at scale. We operate a high-load programmatic infrastructure — processing millions of ad requests per second with sub-200ms response times globally. This isn't a layer on top of someone else's stack; it's built from the ground up, in-house, by the team you'd be joining. Founded in 2012 and headquartered in London, we now have 400+ people across 19 cities and have sustained 40% revenue CAGR since 2018. The engineering problems here are real, the ownership is genuine, and the scale is significant. The opportunity You'll own manual and exploratory testing across LoopMe's Android and iOS SDKs, playing a key role in quality decisions from feature definition through to release. Working closely with developers, automation engineers, and product managers, you'll define test strategies for new features and help shape how quality is approached as our SDK portfolio grows. This role sits within the Mobile SDK Quality team. What you'll do Design, write, and execute manual test plans and test cases for Android and iOS SDK releases and new feature work Own exploratory, regression, and smoke testing across nightly builds and release candidates Validate Adapter Certification builds across multiple OS versions and device configurations Log, triage, and track defects in JIRA with clear reproduction steps and supporting evidence Manage and maintain test cases in TestRail, keeping coverage current across all SDK projects Partner with the automation team to identify high-value candidates for automated test coverage Participate in sprint ceremonies and contribute to quality sign-off decisions Advocate for quality best practices and drive process improvements as the team scales What you'll bring Essential: 2+ years in a QA or mobile testing role Experience testing Android and iOS applications Proficiency with TestRail or a comparable test management system, and JIRA for bug tracking and sprint management Solid understanding of API testing concepts Experience working within Agile/Scrum teams, including use of Charles Proxy or a similar tool for network traffic analysis Nice to have: Familiarity with BrowserStack or a similar real-device cloud platform Experience with Maestro for mobile UI testing Knowledge of AI tools, including Claude Basic scripting ability in Rust or JavaScript Adtech or programmatic advertising domain knowledge What we offer Hybrid working — flexible schedule 1 month work-from-anywhere Annual performance bonus Multikafeteria (sport/culture card) LoopMe Gives Back Learning & development support

🏢 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: The role involves developing and maintaining high-performance backend systems for advertising and e-commerce platforms, focusing on scalable microservices and real-time data processing using Kotlin and Spring Boot. You will design low-latency services, contribute to system architecture, and support production environments in a high-scale setting. The position also emphasizes AI-assisted development practices and collaboration within engineering teams. 🗂️ Requirements: 3+ years of backend development experience, Very good knowledge of Kotlin, Very good knowledge of Spring Boot, Hands-on experience with microservices architecture, Experience with NoSQL databases, Experience with MongoDB, Experience building and maintaining backend systems and APIs, Understanding of system design and scalable architecture, Experience with high-performance and high-scale systems, English B2 level, Polish C1 level, Work permit in the European Union, Openness to occasional visits to Warsaw office, Experience using AI-powered coding assistants 📃 Skills: Kotlin, SpringBoot, MongoDB, NoSQL, Microservices, REST, APIs, GenAI, Claude, GitHubCopilot, Cursor, AWS, Azure 🏢 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 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. 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 Android engineering role focused on building and optimizing mobile ad monetization infrastructure for AI-powered consumer applications. The position involves integrating mediation SDKs, improving ad delivery performance, and developing scalable monetization systems in collaboration with backend, analytics, and AI teams. Offers fully remote B2B work with responsibility for revenue-generating infrastructure used by millions of users. 🗂️ Requirements: 5+ years of Android development experience, Strong Kotlin skills, Strong Java skills, Deep understanding of Android SDK, Knowledge of Android app lifecycle, Experience with AppLovin MAX, Experience with Google AdMob, Experience with Unity LevelPlay, Experience optimizing ad loading performance, Experience with latency optimization, Experience with multithreading, Familiarity with Firebase, Familiarity with Remote Config, Familiarity with Analytics, Familiarity with Crashlytics, Familiarity with BigQuery, Experience with REST APIs, Experience with backend-driven configurations 📃 Skills: Android, Kotlin, Java, AppLovin, AdMob, Unity, LevelPlay, Firebase, RemoteConfig, Analytics, Crashlytics, BigQuery, REST, SDK, Multithreading, RTB, CI/CD 🏢 Description: Senior Mobile Ad Monetization Engineer (Android) About our client Our client is a fast-growing, profitable mobile app company building AI-powered consumer applications used by millions of users worldwide. About the role We are looking for an experienced Senior Mobile Ad Monetization Engineer to build, optimize, and maintain the advertising infrastructure across our client's Android applications. This is a hands-on position focused on developing high-performance ad delivery systems, improving SDK integrations, reducing latency, and maximizing advertising revenue. You will work closely with product, backend, analytics, and AI teams to deliver scalable monetization solutions without compromising the user experience. What you will do Design, develop, and maintain the mobile advertising infrastructure. Integrate and manage multiple mediation SDKs, including AppLovin MAX, Google AdMob, and Unity LevelPlay. Develop advanced ad loading, caching, preloading, and request management mechanisms. Optimize key monetization metrics: Fill Rate, Match Rate, Show Rate, Impression Rate, eCPM, and overall revenue. Build intelligent ad selection, placement logic, and Remote Config fallback systems. Optimize memory usage, threading, lifecycle management, and SDK initialization performance to reduce crashes, ANRs, and latency. Build internal debugging, logging, and telemetry tools, alongside A/B testing infrastructure. Collaborate with backend engineers on server-driven monetization. What we expect 5+ years of commercial Android development experience. Strong programming skills in Kotlin and Java . Deep understanding of the Android SDK and app lifecycle. Proven experience integrating mediation platforms (AppLovin MAX, AdMob, Unity LevelPlay, or Google Ad Manager). Experience optimizing ad loading performance, latency, and multithreading. Familiarity with Firebase, Remote Config, Analytics, Crashlytics, and BigQuery. Experience with REST APIs and backend-driven configurations. Nice to have: Custom mediation adapters, RTB (Real-Time Bidding), server-driven monetization, AI-based optimization, and CI/CD. What is offered Salary: €4,600 - €7,000 per month, depending on experience. Type of work: 100% remote. Contract type: B2B contract (invoicing Optiveum Poland). What else is offered: You will own critical, revenue-generating infrastructure in a profitable startup. You get full remote flexibility and the chance to build technology used by millions. (Note: This is a pure B2B contract with a high base rate; no additional corporate perks are provided).

🏢 Summary: Role focused on owning and expanding automated test suites for Android and iOS SDKs within a high-scale mobile advertising platform. The position involves building mobile UI automation, integrating tests into CI/CD pipelines, and ensuring reliable test execution across real devices and environments. You will work closely with the Mobile SDK team to improve test coverage, stability, and deployment confidence. 🗂️ Requirements: 4+ years in automation engineering or 2+ years as SDET or developer, Strong JavaScript for test automation, Proficiency in Bash and Shell scripting, Experience with GitHub Actions for CI/CD, Experience with BrowserStack or similar real-device cloud platform, Proficiency with Maestro for mobile UI automation, Experience with Allure Reports, Experience with JIRA, Experience building automated test suites for Android and iOS 📃 Skills: JavaScript, Bash, Shell, GitHub, Actions, BrowserStack, Maestro, Allure, JIRA, Android, iOS, Firebase, Rust, TypeScript 🏢 Description: About LoopMe LoopMe is an AI company solving one of advertising's hardest problems: making brand advertising actually measurable — and making it perform. Our platform runs patented machine learning models across billions of consumer signals in real time, optimising campaigns toward outcomes like purchase intent, brand lift, and foot traffic rather than proxy metrics like clicks. The result is 2–5x better performance than industry benchmarks, at scale. We operate a high-load programmatic infrastructure — processing millions of ad requests per second with sub-200ms response times globally. This isn't a layer on top of someone else's stack; it's built from the ground up, in-house, by the team you'd be joining. Founded in 2012 and headquartered in London, we now have 400+ people across 19 cities and have sustained 40% revenue CAGR since 2018. The engineering problems here are real, the ownership is genuine, and the scale is significant. The opportunity You'll own test automation for LoopMe's Android and iOS SDKs, building and maintaining the suites that determine how fast and confidently we ship. Working alongside our existing automation engineer, you'll integrate deeply with the CI/CD pipeline using GitHub Actions, BrowserStack, and Maestro, and extend coverage as new SDK projects come into scope. This role sits within the Mobile SDK engineering team. What you'll do Build and maintain automated test suites for Android and iOS SDKs using JavaScript, Rust, and Bash/Shell scripting Develop mobile UI automation using Maestro across Android and iOS SDK projects Integrate automated tests into GitHub Actions CI/CD workflows for nightly smoke, regression, and Adapter Certification runs Own test execution and monitoring via BrowserStack App Automate, debugging environment-specific failures across devices and infrastructure Manage and publish test results through Allure Reports, surfacing findings to developers via JIRA and Slack Drive down nightly test run time by parallelising suites across multiple GitHub Actions runners Manage test builds via Firebase App Distribution for Android and iOS Leverage AI tools, including Claude, to accelerate test development and improve coverage and resilience What you'll bring Essential: 4+ years in automation engineering, or 2+ years as an SDET or developer Strong JavaScript skills applied to test automation Proficiency in Bash and Shell scripting, and GitHub Actions for CI/CD integration Experience with BrowserStack or a comparable real-device cloud platform Proficiency with Maestro for mobile UI automation, Allure Reports, and JIRA Nice to have: TypeScript familiarity TestRail or an equivalent test management system Charles Proxy for network traffic analysis Experience with AI-assisted test generation or self-healing frameworks Rust programming experience Adtech or programmatic advertising domain knowledge What we offer Hybrid working — flexible schedule 1 month of work-from-anywhere Annual performance bonus Multikafeteria (sport/culture card) LoopMe Gives Back Learning & development support

🏢 Summary: Backend Engineer role in the Advertising team focused on building and operating high-scale, cloud-native systems and end-to-end ML infrastructure for a real-time marketplace. The position involves developing microservices, data pipelines, and advertising systems using Kotlin/Scala, Spring, Kafka, and big data technologies. You will own services end-to-end in a high-availability environment handling massive traffic and complex distributed challenges. 🗂️ Requirements: Proficiency in Kotlin or Scala, Experience with Spring Boot, Experience with Kafka, Hands-on experience with Apache Airflow, Hands-on experience with Apache Spark, Proficiency in PostgreSQL, Experience with database migrations, Experience designing and integrating APIs, English level B2 or higher 📃 Skills: Kotlin, Scala, Spring, SpringBoot, Kafka, Airflow, Spark, PostgreSQL, BigQuery, Kubernetes, Docker, Consul, GitHub, GitHubActions, React, TypeScript 🏢 Description: About the job Massive Scale : Design, build, and optimize systems that handle thousands of requests per minute. This is high-availability, high-performance engineering in practice. Modern Tech Stack : Work with a world-class, cloud-native environment. Our core technologies include Kotlin, Spring, Kafka, and Kubernetes. We're not shy when it comes to ML too :) True Ownership & Autonomy : We live by a "you build it, you run it" philosophy. You'll join an agile, autonomous team with full ownership of your microservices, from design to deployment. Complex Challenges : From distributed systems and data streaming to algorithmic optimization, you'll tackle the complex backend problems that power a massive, real-time marketplace. End-to-End ML Systems: Bridge the gap between big data and real-time product impact. You’ll build the infrastructure using BigQuery and Apache Spark for offline data processing. You’ll integrate these components with our microservices architecture to create the sophisticated advertising system that powers a personalized user experience. Join the Advertising team! You will have a chance to build Allegro Ads - one of the most visible products on the platform. Your team works closely with the Machine Learning team, creating the best experience for customers. High performance, engineering best practices and great atmosphere in the team guaranteed! Important things for you Flexible working hours in the hybrid model (4/1) - working hours start between 7:00 a.m. and 10:00 a.m. We also have 30 days of occasional remote work. The salary range for this position depending on the skill set is as follows (contract of employment, tax-deductible cost): PLN 18 850 - 25 900 Annual bonus based on your annual performance and company results. Our team is based in Warsaw. We are looking for people who: Code in Kotlin or Scala and have experience with Spring Boot and Kafka to build robust backend systems; Have hands-on experience with Apache Airflow and Spark , enabling them to manage high-velocity data pipelines and build scalable reporting engines; Are proficient in PostgreSQL and have experience with database migrations and designing integrations via APIs; Enjoy close collaboration with Data Scientists and Analysts, working together to implement complex models and turn raw data into actionable insights; Are enthusiastic about AI and want to stay at the forefront of technical innovation; Want to build impactful tools for a diverse range of users, helping them understand campaign performance through advanced statistics and dashboards; Experience with frontend technologies (React/TypeScript) is a “Nice to have” to help build modern frontend reporting components; Are excited to join a growing team where they can influence the technical vision and help shape new projects from the ground up within the ecosystem; Know English at at least B2 level. What's in it for you: Well-located offices (with e.g. fully equipped kitchens, bicycle parking, terraces full of greenery) and excellent work tools (e.g., raised desks, ergonomic chairs, interactive conference rooms). A 16" or 14" MacBook Pro or corresponding Dell with Windows (if you don't like Macs) and all the necessary accessories. A wide selection of fringe benefits in a cafeteria plan - you choose what you like (e.g., medical, sports or lunch packages, insurance, purchase vouchers). English classes that we pay for related to the specific nature of your job. A training budget, inter-team tourism ( see more here ), hackathons, and an internal learning platform where you will find multiple trainings. An additional day off for volunteering, which you can use alone, with a team, or with a larger group of people connected by a common goal. Social events for Allegro people - Spin Kilometers, Family Day, Fat Thursday, Advent of Code, and many other occasions we enjoy. And that's just the beginning! You can read more about the benefits here . #goodtobehere means that: You will join a team you can count on - we work with top-class specialists who have knowledge- and experience-sharing in their DNA. You will love our level of autonomy in team organization, the space for continuous development, and the opportunity to try new things. You get to choose which technology solves the problem and you are responsible for what you create. You will value our Developer Experience and the full platform of tools and technologies that make creating software easier. We rely on an internal ecosystem based on self-service and widely used tools such as Kubernetes, Docker, Consul, GitHub, and GitHub Actions. Thanks to this, you can contribute to Allegro from your very first days on the job. You will be equipped with modern AI tools to automate repetitive tasks, allowing you to focus on developing new services and refining existing ones (also leveraging AI support). You will create solutions that will be used (and loved!) by your friends, family and millions of our customers. You will meet the Allegro Scale , which starts with over 1000 microservices, an open-source data bus (Hermes) with 300K+ rps, a Service Mesh with 1M+ rps, tens of petabytes of data, and production-used machine learning. You will become part of Allegro Tech - We speak at industry conferences, cooperate with tech communities, run our own blog (it's been over 10 years!), record podcasts, lead guilds, and we organize our own internal conference - the Allegro Tech Meeting. We create solutions we love (and can) to talk about! Send us your CV and… see you at Allegro!

🏢 Summary: Backend Java Engineer role focused on developing and modernizing a high-load B2B gaming back-office platform processing millions of real-time transactions daily. The position involves building new features, improving scalability and reliability, and evolving a monolithic system toward distributed services. You will contribute to architectural design, performance optimization, and production issue resolution. 🗂️ Requirements: 5+ years of Java development experience, Strong knowledge of backend architecture, Experience with distributed systems, Experience with relational databases and SQL, Experience with message-driven systems, Experience refactoring production systems, Strong debugging and problem-solving skills, Intermediate English or higher 📃 Skills: Java, Spring, MSSQL, SQL, Kafka, Redis, Microservices 🏢 Description: Role Overview: We are looking for an experienced Java Engineer to join the client's backend team, which is working on the back-office platform of a high-load B2B gaming system. Their platform processes millions of transactions daily and supports real-time operations for multiple partners. As the system continues to grow, the engineering team is expanding to improve scalability, performance, and reliability, while gradually evolving parts of the platform from a monolithic architecture toward distributed services. You will work on both new functionality and architectural improvements, helping modernise critical parts of the platform. Technology Stack: Java 8 / Java 17, Spring Framework, MSSQL 2019, Kafka, Redis, distributed services with parts of the system still evolving from a monolithic architecture. Key Responsibilities: Develop new backend functionality for the platform; Improve system performance, scalability, and reliability; Participate in refactoring and modernisation of legacy components; Contribute to architectural discussions and technical design; Investigate and resolve production issues; Assess technical feasibility and complexity of business requirements; Collaborate closely with backend engineers, technical leads, and product teams Required Skills & Experience: 5+ years of Java development experience; Strong understanding of backend architecture and distributed systems; Experience working with relational databases and SQL; Familiarity with message-driven systems (Kafka or similar); Experience in improving or refactoring existing production systems; Strong problem-solving and debugging skills; Comfortable working in collaborative environments with code reviews and shared ownership of the codebase; English level: Intermediate or higher. The company guarantees you the following benefits: Global Collaboration: Join an international team where everyone treats each other with respect and moves towards the same goal; Autonomy and Responsibility: Enjoy the freedom and responsibility to make decisions without the need for constant supervision; Competitive Compensation: Receive competitive salaries reflective of your expertise and knowledge as our partner seeks top performers; Remote Work Opportunities: Embrace the flexibility of fully remote work, with the option to visit company offices that align with your current location; Flexible Work Schedule: Focus on performance, not hours, with a flexible work schedule that promotes a results-oriented approach; Unlimited Paid Time Off: Prioritise work-life balance with unlimited paid vacation and sick leave days to prevent burnout; Career Development: Access continuous learning and career development opportunities to enhance your professional growth; Corporate Culture: Experience a vibrant corporate atmosphere with exciting parties and team-building events throughout the year; Referral Bonuses: Refer talented friends and receive a bonus after they successfully complete their probation period; Medical Insurance Support: Choose the right private medical insurance and receive compensation (full or partial) based on the cost; Flexible Benefits: Customise your compensation by selecting activities or expenses you'd like the company to cover, such as a gym subscription, language courses, Netflix subscription, spa days, and more; Education Foundation: Participate in a biannual raffle for a chance to learn something new unrelated to your job as part of your commitment to ongoing education. Interview process: HR Interview with the Recruiter; Technical interview with the team; A 2-hour Final interview with the team. If you find this opportunity right for you, don't hesitate to apply or get in touch with us if you have any questions!