NUMBERO , a leading German tech startup revolutionizing after-sales processes in car dealerships, is looking for a Full Stack Engineer (m/f/d) to join our growing development hub in Valencia.
Who We Are
At NUMBERO, our mission is to equip car dealerships with cutting-edge tools to optimize their after-sales operations.
We integrate trusted sources for parts and labor costs, various Dealer Management Systems, and other relevant data sources.
We also leverage metadata analysis to drive intelligent insights.
Headquartered in Germany and supported by a growing international team, we focus on innovation, collaboration, and delivering outstanding value to our clients.
Our Valencia office plays a key role in shaping the future of our technologies and services.
About The Role
We are looking for a versatile Full Stack Engineer with strong backend and data engineering skills.
You will work across a Node.js backend, React and TypeScript frontend, and data platforms such as Databricks, supporting data pipelines, integrations, analytics, and AI-driven features.
The role requires end-to-end ownership, from database and API design through frontend delivery, deployment, and monitoring.
You should be comfortable working across application development, data workflows, job queues, migrations, authentication, and production systems.
Core Responsibilities
- Develop and maintain web application features across the full stack (React + TypeScript frontend, Express.js + TypeScript backend)
- Design and implement database schemas, migrations, and optimized queries (MySQL / MariaDB)
- Build and maintain REST APIs and integrate them with frontend systems
- Work with background job processing, scheduled tasks, and asynchronous workflows
- Contribute to AI-driven features, LLM integrations, and prompt engineering
- Integrate web applications with data platforms (PowerBI, Databricks, Azure Data Lake Storage)
- Ensure scalable, secure, and production-ready implementations
- Maintain high test coverage and participate in code reviews
- Monitor and debug production systems independently
- Collaborate with technical and business stakeholders
Required Technical Skills
Frontend & Web
- Strong expertise in React + TypeScript
- Advanced HTML5 / CSS3 (Bootstrap, Tailwind CSS)
- REST API design and consumption
- Git version control
Backend & Infrastructure
- Solid experience with Node.js + Express.js
- MySQL / MariaDB - schema design, query optimization, connection pooling, migrations
- Redis - caching, job queues, distributed locking
- Background job processing (BullMQ or similar queue systems)
- Docker - containerization, multi-stage builds, Docker Compose
- JWT authentication and role-based access control
- Scheduled task management (cron jobs)
Data & Cloud
- Practical experience with Databricks and Azure Data Lake Storage (ADLS)
- Understanding of data pipelines and structured/unstructured data handling
- Experience integrating web applications with data platforms (PowerBI, Databricks, ADLS)
- Familiarity with Azure services (Azure AD, Static Web Apps, or similar)
- Understanding of data synchronization pipelines and ETL processes
AI & Prompt Engineering
- Understanding of AI-driven applications and LLM integrations
- Ability to design, test, and refine prompts for reliable AI outputs
- Experience working with AI APIs (OpenAI, Azure AI, Anthropic, etc.)
Code Quality & Security
- Writing and maintaining unit tests (Jest, Supertest)
- Maintaining high test coverage standards (95%+ preferred)
- Input validation and schema enforcement (Joi or similar)
- Awareness of OWASP Top 10, rate limiting, CORS, and secure authentication flows
Nice To Have
- PowerBI API integration and DAX queries
- E2E testing frameworks (Cypress, Playwright)
- PDF generation pipelines (pdf-lib, Puppeteer)
- Email automation systems (Nodemailer, templated dispatch)
- Prometheus / Grafana monitoring
- Azure Static Web Apps or similar deployment platforms
- CI/CD pipeline configuration
Experience With Scalable Cloud Architecture (Azure Preferred)
UI/UX design awareness
Soft Skills
- High ownership mentality - you treat features as yours from start to finish
- Professional and structured communication
- Strong problem-solving ability
- AI-adaptive mindset - comfortable working with rapidly evolving technologies
- Team-oriented but capable of independent execution
Requirements
- Production-aware - you think about what happens after deployment
- Professional experience of at least 3 years (mandatory)
- English - Fluent (mandatory)
- Spanish - Fluent (mandatory)
- German - Nice to have
WHY IT'S A GREAT IDEA TO JOIN US
- Plenty of room to bring your ideas to life
- Modern work atmosphere and office equipment
- Company events and activities
- Open company culture with flat hierarchies
- Always the latest hardware
- Flexible working hours
- Competitive salary based on your experience
- Supportive team spirit
- Thorough onboarding
- Permanent full-time position
- Access to coaching programs
- Career development opportunities