Back End Developer

Hybrid role: 3 days per week at the office in Valencia (Spain) At Principal33 we strive to make happiness at work a reality. Because it's not just about the money, it's also about the work environment and appreciation. It's about creating the best team setup you can imagine and getting involved in the things you're passionate about. And you can be a part of it, because it's fun to get things done We want our employees to innovate and we allow them to do what they are truly passionate about. Based on this conviction, Principal33 aligns its strategy around its vision: to become a leading IT service company and a better working-life balance. With currently around 200 employees from different countries, we are actively shaping the future of work. As a Backend Developer you will play a key role in building robust, scalable systems that support AI-driven products operating in real time. We are looking for someone who combines strong technical expertise with ownership, system-level thinking, and collaboration. You will work on an AI-powered video analytics platform focused on real-time detection and alerting . The platform processes live video streams and generates alerts when predefined events occur. Your work will ensure that the backend systems are secure, reliable, and ready to scale as the platform grows. Key Responsibilities Design, develop, and maintain backend services in C# (.NET Core) for the SaaS platform Design and manage database schemas and data access layers using Entity Framework Core , ensuring performance and data integrity Build and maintain secure, well-documented REST APIs consumed by frontend and other services Implement backend business logic using DDD and Clean Architecture principles , ensuring clean separation of concerns Design and operate microservice-based and event-driven systems , including inter-service communication via Apache Kafka Implement authentication and authorization (RBAC) using ORY Kratos & ORY Keto , ensuring secure access control Support real-time system behavior and live updates using SignalR where applicable Collaborate with frontend, AI, and platform teams to design and integrate end-to-end features Ensure backend systems meet high standards of scalability, reliability, security, and observability Write and maintain unit and integration tests to ensure system stability and correctness Participate in architectural decisions and contribute to the long-term evolution of the backend platform Requirements Must-Have Qualifications Strong professional experience as a Backend Developer working with C# and .NET Core Proven experience in database design and data access using Entity Framework Core or equivalent ORMs Hands-on experience building secure REST APIs for production systems Solid understanding and practical application of DDD and Clean Architecture in backend development Experience implementing authentication and authorization , including role-based access control (RBAC) Familiarity with ORY Kratos and ORY Keto , or similar identity and authorization systems Experience working with microservices and inter-service communication , including Apache Kafka Exposure to real-time systems and technologies such as SignalR Strong experience writing and maintaining unit and integration tests Ability to collaborate effectively with cross-functional teams and communicate technical concepts clearly Nice-to-Have Experience working in event-driven architectures and distributed systems Exposure to Python services within a heterogeneous backend ecosystem (REST APIs, Kafka-based communication) Experience supporting AI-driven, data-intensive, or video analytics platforms Background in SaaS products operating in high-availability or mission-critical environments What we offer Benefits Flexible work hours Private medical insurance Day off on your birthday Referral bonus if you bring your contacts Gifts for special occasions Office that takes care of your well-being and on top of all we are pet friendly, bring your pet to the office Fridge full of snacks at the office, healthy ones and not so healthy as well International and multicultural environment (Self)-Development Continuous training, we will help you improve your technical skills, evolve in the tech community and develop as a professional. We are an active part of the tech-community. You may have the opportunity to attend and participate in local and international tech-events. Wanna join?