Full Stack Engineer

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 AREAt 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 ROLEWe 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 RESPONSIBILITIESDevelop 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 systemsWork with background job processing, scheduled tasks, and asynchronous workflowsContribute to AI-driven features, LLM integrations, and prompt engineeringIntegrate web applications with data platforms (PowerBI, Databricks, Azure Data Lake Storage)Ensure scalable, secure, and production-ready implementationsMaintain high test coverage and participate in code reviewsMonitor and debug production systems independentlyCollaborate with technical and business stakeholdersREQUIRED TECHNICAL SKILLSFrontend & WebStrong expertise in React + TypeScriptAdvanced HTML5 / CSS3 (Bootstrap, Tailwind CSS)REST API design and consumptionGit version controlBackend & InfrastructureSolid experience with Node.js + Express.jsMySQL / MariaDB - schema design, query optimization, connection pooling, migrationsRedis - caching, job queues, distributed lockingBackground job processing (BullMQ or similar queue systems)Docker - containerization, multi-stage builds, Docker ComposeJWT authentication and role-based access controlScheduled task management (cron jobs)Data & CloudPractical experience with Databricks and Azure Data Lake Storage (ADLS)Understanding of data pipelines and structured/unstructured data handlingExperience 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 processesAI & Prompt EngineeringUnderstanding of AI-driven applications and LLM integrationsAbility to design, test, and refine prompts for reliable AI outputsExperience working with AI APIs (OpenAI, Azure AI, Anthropic, etc.)Code Quality & SecurityWriting 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 flowsNICE TO HAVEPowerBI API integration and DAX queriesE2E testing frameworks (Cypress, Playwright)PDF generation pipelines (pdf-lib, Puppeteer)Email automation systems (Nodemailer, templated dispatch)Prometheus / Grafana monitoringAzure Static Web Apps or similar deployment platformsCI/CD pipeline configurationExperience with scalable cloud architecture (Azure preferred)UI/UX design awarenessSOFT SKILLSHigh ownership mentality - you treat features as yours from start to finishProfessional and structured communicationStrong problem-solving abilityAI-adaptive mindset - comfortable working with rapidly evolving technologiesTeam-oriented but capable of independent executionProduction-aware - you think about what happens after deploymentREQUIREMENTSProfessional experience of at least 3 years (mandatory)English - Fluent (mandatory)Spanish - Fluent (mandatory)German - Nice to haveWHY IT’S A GREAT IDEA TO JOIN USPlenty of room to bring your ideas to lifeModern work atmosphere and office equipmentCompany events and activitiesOpen company culture with flat hierarchiesAlways the latest hardwareFlexible working hoursCompetitive salary based on your experienceSupportive team spiritThorough onboardingPermanent full-time positionAccess to coaching programsCareer development opportunitiesHOW TO APPLYStill reading? Great! Ready to become part of our mission? As we are looking for someone with a good drive, our hard skill requirements are not too strict. What really matters to us is that you bring your own drive and are eager to make a difference.Send your CV to with the subject line “Full Stack Engineer”. We look forward to meet you!

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 *Production-aware - you think about what happens after deployment REQUIREMENTS *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

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.