Rosen Petrov

● Developed a HIPAA-compliant RCM system integrating HL7 and FHIR APIs for real-time interoperability, streamlining billing, claims processing, and regulatory compliance in healthcare. ● Developed scalable and high-performance microservices using Node.js (NestJS) and Python (FastAPI), while building efficient inter-service communication using RabbitMQ. ● Built GraphQL APIs using Node.js (Apollo Server) and Python (Graphene), enabling efficient data fetching and seamless integration with a React frontend (Apollo Client) for an optimized user experience. ● Designed and built an authentication microservice using Node.js and TypeScript, implementing OIDC, SSO, JWT authentication, and 2FA (Email OTP) for secure user access. Deployed the service to AWS Lambda with AWS API Gateway, managing infrastructure using AWS CDK for scalability and maintainability. ● Designed and built a robust React/Next.js infrastructure with a scalable component architecture, leveraging React Hooks, TypeScript, Redux-Toolkit, and Tailwind CSS. Utilized Storybook for isolated component development and implementing SSR, SSG, and ISR for optimal performance and SEO. ● Implemented unit and integration tests for React applications using Jest and React Testing Library, ensuring 80%+ test coverage, improving component reliability, and preventing regressions. ● Streamlined CI/CD workflows with Docker and Kubernetes, cutting deployment times and ensuring that critical updates and security patches were delivered without disrupting active trials. ● Mentored junior developers through code reviews, pair programming, and knowledge-sharing sessions, improving team efficiency by 30% while maintaining comprehensive API documentation using Swagger/OpenAPI.

● Migrated a legacy monolithic application to a scalable microservices architecture, enhancing system modularity, scalability and maintainability while implementing key design patterns such as Strangler, Database-per-Service, API Gateway, Saga and CQRS for efficient service communication and transaction management. ● Built a scalable full stack booking application using React 18 and Django REST Framework, integrating Celery and Redis for asynchronous task processing, while deploying on GCP with Cloud Run and Firestore, enabling real-time scheduling, payment processing, and automated notifications. ● Designed and deployed scalable serverless architectures for SaaS-based B2B and B2C applications using AWS Lambda, API Gateway, AWS AppSync, and DynamoDB, integrating AWS IAM for secure access control, while ensuring high availability, cost efficiency, and seamless auto-scaling. ● Designed and managed scalable infrastructure with AWS CDK and CloudFormation, streamlining deployments faster and more reliable across different environments. ● Optimized performance and cost by reducing cold start latency, using SQS & SNS for asynchronous processing, and implementing caching strategies with DynamoDB Accelerator (DAX) and Redis. ● Demonstrated strong problem-solving, communication, and collaboration skills, effectively working with cross-functional teams to deliver scalable solutions, streamline workflows, and drive project success in fast-paced environments.

● Worked with several clients for building and maintaining Social Media platforms, E-Commerce applications and FinTech solutions, using Node.js, Python, Java, React and Angular. ● Managed Firestore and Firebase Authentication on GCP, optimizing database performance, securing user authentication, and ensuring seamless integration with cloud services for scalable and reliable applications. ● Built high-performance RESTful APIs using Node.js (Express.js) and Python (Django, Flask), integrating Sequelize, TypeORM, and Django ORM to efficiently manage SQL databases and streamline data operations. ● Optimized frontend performance by reducing page load times, minimizing server requests, and implementing code-splitting, lazy loading, and optimized asset delivery, achieving a 40% improvement in page load speed and boosting Core Web Vitals scores. ● Optimized search and analytics capabilities by integrating Elasticsearch with MongoDB, implementing efficient indexing, query tuning, and real-time data synchronization for faster and more accurate search results. ● Configured and optimized Cloudflare and Nginx for secure, high-performance web applications, implementing CDN caching, DDoS protection, load balancing, and reverse proxy setups to enhance speed, security, and scalability. ● Collaborated with DevOps engineers to optimize and support CI/CD pipelines using GitHub Actions and Jenkins, streamlining automation and deployment processes for enhanced efficiency and reliability.

● Collaborated with designers and senior developers to convert UI/UX mockups into clean, responsive, and accessible web interfaces using HTML, CSS, and JavaScript, and developed Single Page Applications (SPAs) using AngularJS and React class components. ● Engineered backend functionality using Python, improving data processing efficiency by 25% through the application of object-oriented design, SOLID principles, and optimized data structures and algorithms. ● Gained hands-on experience with AWS and GCP by leveraging services such as EC2, S3, Lambda, Cloud Functions, BigQuery, and Firestore to deploy, manage, and scale cloud-based applications for performance and reliability. ● Developed practical experience in cross-functional team collaboration, problem-solving, and agile methodologies, adapting to fast-paced development environments.