Senior Full Stack Engineer

Senior Full Stack Engineer Note: While this is a remote role, applicants must be form Croatia, Serbia or Bosnia and Herzegovina to be considered. Are you a JavaScript engineer who thrives on understanding how things work under the hood rather than just gluing framework APIs together? Do you get excited about low-level engine mechanics, browser internals, and designing resilient, high-availability systems that handle serious data volumes? We value a go-getter attitude, a drive to get things done, and the empathy to truly understand our clients’ needs. Our team takes pride in working hard – and having fun while doing it. We believe in the power of collaboration and bringing like-minded people together to build great things. Your role As a Senior Full Stack JavaScript Engineer, you will design, build, and maintain high-availability systems handling large data volumes with strict uptime requirements. You will take ownership of backend services end-to-end, drive core system architectures, and ensure high engineering standards across the stack. We are looking for an engineer who possesses a deep, foundational understanding of core JavaScript and TypeScript principles without relying heavily on abstract frameworks. You know what happens under the hood, from browser mechanics to backend runtime execution and you bring strong Computer Science fundamentals to solve complex scalability and performance challenges. Tech stack & Core concepts Languages/Frameworks: Modern JavaScript (Vanilla JS), TypeScript, Node.js Architecture & Backend: Distributed Systems, Event/Data Streaming (Kafka, Kinesis, etc.), Messaging Queues (RabbitMQ, SQS, etc.) DevOps & Infra: Docker/Containers, CI/CD pipelines, Infrastructure as Code (IaC) Fundamentals: D ata structures, algorithms, browser engines/inner workings What we expect Core technical expertise Vanilla JavaScript & TypeScript Deep Understanding: True mastery of core JS/TS concepts, event loops, memory management, and browser inner workings beyond just using framework-level abstractions. High Availability & Distributed Systems: Proven, hands-on experience designing, building, and operating high-availability backend systems in production handling large data volumes. Event & Message Architectures: Strong familiarity with event/data streaming technologies (e.g., Kafka, Kinesis) or message queue systems (e.g., RabbitMQ, SQS). DevOps Ownership: Comfortable with containerization, building modern CI/CD pipelines, and working with Infrastructure as Code. Ways of working LLM Tooling & AI-Assisted Development: Good leverage of LLM tools (e.g., Claude Code, Cursor, GitHub Copilot) to enhance productivity within your daily engineering workflow. Engineering Excellence: Ability to take complete ownership of complex subsystems, mentor team members, and communicate technical decisions clearly. Optional Advantage (nice to have) Experience with performance optimization at scale. Prior involvement in architecting event-driven microservices architectures. A CS degree (or equivalent practical experience) with a solid grasp of core data structures (e.g., binary trees, hash maps) and the ability to articulate trade-offs and real-world application scenarios. What we offer Choose how you work: Remote-first culture with the option to work remotely, hybrid, or on-site (Croatia, Serbia, or Bosnia and Herzegovina). Flexible working hours: Balance your work and life on terms that suit you best. Growth & Mentorship: Opportunity to work on complex, high-scale global projects with modern tools and continuous learning opportunities. Comprehensive Healthcare: Private health insurance and 100% paid sick leave. Financial Perks: Third-pillar retirement savings, referral rewards, seasonal bonuses, and travel allowances. Well-being & Community: Subsidized sports cards (MultiSport/PassSport), internal workshops, meetups, and team-building events. Salary range Senior Full Stack JS Engineer: Up to €5,000 gross 1 (dependent on experience and technical interview performance) Sounds exciting? Click on the button below and apply now. 😊 Locations Zagreb Remote status Fully Remote Zagreb About Q Ltd. We are an award-winning software and design agency. With 350+ full-time experts, we provide services and solutions to cover all phases of the digital product life-cycle. Working in various industries across 20 countries worldwide, we exceed our boundaries each day.