Backend Engineer (Medior)

Backend Engineer (Medior)

ZirconTree is changing the way media agencies and marketing teams work with real-time bidding (RTB). Our SaaS system connects global platforms into one intuitive solution that enables efficient campaign launch and AI-generated media planning. We offer both self-service and managed-service models for agencies and brands alike.

SK/CZ + Global Opportunities

Bratislava/Prague (Hybrid or Remote)

Work Location

Mid/Senior

Seniority level

Full-time, freelance

Employment type

Role overview

We are looking for a Mid-level Backend Engineer to join our team and contribute to the development of an AdonisJS (TypeScript) backend, API design for frontend applications, database modeling, and performance and security optimization.

We expect experience with backend development (e.g. Java, Node.js), databases, and a strong willingness to learn, grow, and collaborate closely with frontend and other teams.

Do you want to build solutions that our clients use every day and that genuinely simplify their work? Keep reading. 👇

Your mission

Your responsibility will be to ensure that our backend systems are stable, secure, and performant.

You will maintain and extend the backend (AdonisJS).

Prepare APIs for the frontend, and design appropriate database indexes and migrations.

What we expect from you

Experience with AdonisJS (controllers / services / models), Knex migrations, transactions.

Input validation (Zod / Joi), data sanitization, error normalization.

N+1 query prevention, indexing, pagination.

PostgreSQL basics, Sentry / log levels, correlation IDs.

Security best practices: CORS, rate limiting, CSRF protection, input sanitization.

Nice to have: OpenAPI/Swagger, testing (Jest/Supertest), OpenTelemetry (otel).

Our mindset

Transparency, trust, and honest communication.

Focus on results, efficiency and quality.

Initiative, ownership, and a growth mindset.

Collaboration and team support.

Continuous improvement and curiosity.

We at Zircon Tree believe that the way we work is just as important as the result. Therefore, we expect all team members to share and develop these values.

Benefits

Remote work and flexible working hours

Original offices and a friendly atmosphere

Dynamic environment of a fast-growing innovative company

Multisport card and sick days

Career development, training courses, workshops, and conferences

Team buildings, positive energy, and a real work–life balance

How to let us know you're interested

Send us your CV and a short cover letter (or a 2-minute video) to careers@zircontree.com and include your consent for personal data processing.

Consent for Personal Data Processing:

I hereby give my consent to ZirconTree s.r.o. to process my personal data provided in my CV and cover letter for the purposes of participating in the selection process and maintaining record of applicants, in accordance with Act No. 18/2018 Coll. on Personal Data Protection and GDPR. This consent is granted for a period of 12 months and may be withdrawn at any time in writing.