Fullstack Developer

Billennium; Poland; Hybrid; PLN 180,000 - 240,000; Full time

Benefits offered by this job

Udemy for Business

Private medical care

Multisport card

Language lessons

Shopping vouchers

Job summary

Billennium is seeking a Full Stack Engineer to own the frontend experience in Angular, while being capable of backing changes in the backend to unblock the team.

You will collaborate with Backend, DevOps, and product stakeholders to deliver scalable, reliable, and high-performance products end-to-end, from UI to API.

Qualifications

• 3+ years of frontend or fullstack engineering experience.
• Strong proficiency in Angular and Lit HTML.
• Experience integrating with APIs and microservices; understand HTTP/REST, auth flows, and error handling.
• Working proficiency in Python; able to navigate a FastAPI codebase and modify endpoints.
• Familiarity with relational databases (MySQL/PostgreSQL) and SQL.
• Experience with Docker-based workflows and cloud-native environments.

Responsibilities

• Design, develop, and maintain frontend components in Angular (and Lit HTML).
• Own the frontend-backend integration through OpenAPI-defined APIs.
• Make targeted backend changes to ship features without always relying on a backend engineer.
• Contribute to full-stack architecture discussions and API design decisions.
• Participate in code reviews and maintain code quality across frontend and backend.

Skills

Angular

Lit HTML

REST APIs

Frontend architecture

Code reviews

Mentoring

Tools

Docker

FastAPI

SQLAlchemy

MySQL

PostgreSQL

OpenAPI

AWS

Job description

Billennium is a global technology company with over 20 years of experience, committed to innovation and empowering businesses. As an employer, we offer a supportive, growth-focused environment where collaboration and creativity thrive. Join us to shape the future of technology together!

As a Full Stack Engineer, you will take primary ownership of our frontend experience while being capable of making the backend changes needed to unblock yourself and your team. You'll work closely with Backend Engineers, DevOps Engineers, and stakeholders to deliver scalable, reliable, and high-performance products end-to-end, from pixel to API.

What you will do:

• Design, develop, and maintain frontend components in Angular (and Lit HTML where applicable), ensuring optimal performance, responsiveness, and usability.
• Own the integration layer between frontend and backend: consume and contribute to OpenAPI-defined APIs, handle data contracts, and wire up microservices cleanly.
• Make targeted backend changes, new endpoints, tweaks to existing services, minordata model updates, so you can ship features without always depending on a dedicated backend engineer.
• Contribute to architectural discussions across the full stack, from UI component structure to API design and data access patterns.
• Participate actively in code reviews, providing feedback on both frontend and backend code quality, adherence to standards, and performance.
• Mentor and support junior engineers across the stack.
• Stay current with evolving frontend and full-stack best practices.

What success in the first 6 months looks like:

• You've built trust with Backend, DevOps, and Product peers and taken clear ownership of 2-3 frontend domains, including their design system consistency and API integration contracts.
• You've delivered frontend features end-to-end, from UX design discussion through Angular implementation, API wiring, tests, and documentation, without needing hand-holding at either layer.
• You've unblocked yourself (and others) by making safe, well-reviewed backend changes: adding an endpoint, adjusting a response model, or optimising a query, rather than waiting in a queue.
• You've raised frontend quality: responsive across devices, accessible, consistent with our design system, and validated against real API contracts rather than mocks.
• You've contributed to meaningful observability on the frontend, error tracking, performance budgets, and linked them to backend SLIs where relevant.
• You've shared knowledge through documentation, code reviews, and mentoring, so the team's frontend capability grows with you.

What we are looking for:

• 3+ years of experience in frontend or fullstack engineering.
• Strong proficiency in Angular and experience with component-based frameworks such as Lit HTML.
• Solid understanding of responsive design, UX/UI principles, and a keen eye for design detail.
• Proven experience integrating with APIs and microservices, you understand HTTP, REST conventions, auth flows, and error handling deeply.
• Working proficiency in Python, enough to navigate a FastAPI codebase, add or adjust endpoints, and write Pydantic models and SQLAlchemy queries.
• Familiarity with relational databases (MySQL/PostgreSQL) at the query and schema level.
• Experience with containerised workflows using Docker.
• Excellent problem-solving skills; comfortable working independently and collaboratively.
• Strong English communication skills and ability to work across disciplines.
• Comfortable using AI-assisted development tools (e.g. Claude Code, Cursor, or similar) as part of daily workflow.
• Familiarity with LLM API integration (OpenAI, Anthropic, or similar) and an understanding of the UX patterns specific to AI-powered features.

We're fully cloud-native on AWS, with a lean, API-first product development approach.

Perks and benefits:

• Comprehensive benefits - enjoy Udemy for Business, private medical care, Multisport card, veterinary package, language lessons, and shopping vouchers.
• Flexibility - adaptable working hours and remote/hybrid work options to suit your lifestyle & location.
• Career growth - access opportunities for professional development and learning, including perks related to our official partnerships with global IT giants: Microsoft, AWS, Snowflake, Salesforce & more.
• Global collaboration - work with a diverse, international team.
• Innovative environment - be part of a forward-thinking and growth-oriented workplace.
• Engaging community - Work with passionate professionals and participate in team-building events, hackathons, and CSR initiatives to make an impact beyond work.
• Team-building events including our company tradition (annual company event in Mazury).
• A pleasant surprise to start your journey with us in the form of a welcome pack.

Recruitment process:

• HR call
• Technical Interview
• Interview with the dedicated Client