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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Full Stack Engineer - **Company:** Numbero Spain S.l. - **Location:** Madrid, Spain - **Contract:** Permanent contract - **Skills:** JavaScript (Programming Language), Application Programming Interfaces (APIs), Artificial Intelligence, Data Analysis, HTML5, User Authentication, Unit Testing, Microsoft Azure, Bootstrap (Software), Cascading Style Sheets (CSS), Cloud Computing, Cloud Engineering, Code Coverage, Software Quality, Code Review, Databases, Continuous Integration, Cross-Origin Resource Sharing (Ajax Programming), Cron, Data Validation, Information Engineering, Extract Transform Load (ETL), Data Synchronization, Database Schema, Software Debugging, Design of User Interfaces, MariaDB, Automation of Marketing, MySQL, Node.Js, Open Web Application Security, Query Optimization, Role-Based Access Control, Redis, E2e Testing, Power BI, Azure Active Directory, Prometheus, Azure Data Lake, Software Engineering, Systems Integration, TypeScript, Unstructured Data, Web Applications, Tailwind, ReactJS, Large Language Models, Express.js, Grafana, Prompt Engineering, Cypress (Programming Language), Caching, Puppeteer (Software), Backend, Rate Limiting, Git, Containerization, Playwright, Data Management, Front End Software Development, Virtual Agents, Api Design, Restful APIs, Data Pipelines, Docker, Databricks - **Published:** September 29, 2026 - **Apply:** https://www.buscojobs.com.es/full-stack-engineer-en-madrid-ID-373349806 ## About the Role We are looking for a versatile Full Stack Engineer with strong backend and data engineering skills., 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 ## Description 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 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 SkillsFrontend & WebStrong expertise in React + TypeScript Advanced HTML5 / CSS3 (Bootstrap, Tailwind CSS) REST API design and consumption Git version control Backend & InfrastructureSolid 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 & CloudPractical 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 EngineeringUnderstanding 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 & 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 flows Nice To HavePowerBI 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 SkillsHigh 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 RequirementsProduction-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 USPlenty 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#J-*****-Ljbffr ## Related Videos - [How a Small Team Shrank a Microsoft Monorepo by 94%](https://www.wearedevelopers.com/videos/1236-how-a-small-team-shrank-a-microsoft-monorepo-by-94) - 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