Senior Fullstack Engineer – React and Kotlin Specialists

Unleash innovation — design the future of intelligent advertising ecosystems! Warszawa-based opportunity with hybrid work model.As a Senior Fullstack Engineer – React and Kotlin Specialists, you will be working for our client, a leader in building advanced advertising tools, focusing on creating intelligent recommendation systems and automating campaign management for advertisers on Allegro Ads. Join a mission-driven project that revolutionizes how businesses grow through cutting-edge technology and data-driven insights, offering exciting avenues for professional growth and innovation. Your main responsibilities: • Develop and maintain backend services using Kotlin, integrating machine learning-driven recommendation engines in collaboration with data science teams. • Build scalable, event-driven architectures to process large data volumes within cloud environments, leveraging GCP. • Design and implement high-performance APIs to support analytical dashboards and market benchmarks. • Create and optimize scalable microfrontends using React, prioritizing accessibility and server-side rendering for analytical tools. • Collaborate with cross-functional teams to deliver seamless, secure, and efficient software solutions. • Ensure high code quality through testing frameworks such as Jest, Vitest, or Playwright, with a focus on performance and reliability. • Contribute to evolving microservice architectures, utilizing Spring Boot, MongoDB, SQL, and cloud-native tools. • Participate actively in code reviews, sprint planning, and technical discussions to foster continuous improvement. You're ideal for this role if you have: • At least 3 years of experience in full-stack development, with a focus on React and Kotlin. • Strong proficiency in TypeScript, React, HTML/CSS, and backend technologies like Kotlin, Spring Boot, and microservices. • Experience working with cloud ecosystems, preferably GCP. • Solid understanding of database management, including MongoDB and SQL. • Familiarity with event-driven architectures and large-scale data processing. • Ability to communicate effectively in Polish and English. • Experience working in an Agile environment with a focus on delivering high-quality software. It is a strong plus if you have: (optional) • Certifications related to GCP or microservices architecture. • Experience with agentic coding tools like Copilot/OpenCode. • Knowledge of accessibility standards (a11y) and performance optimization techniques. Language Required for the role: • Polish (Communicative) • English (Communicative) Eligibility for this role: • Only candidates with an existing legal right to work in the European Union will be considered for this role. #MAKEYourCareerBETTER Interested? Apply now and include your CV (preferably in English) along with a statement confirming your consent to the processing and storage of your personal data.