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.

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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.