Designed and developed backend components for LINK-SEGURO, an email notification platform for mass communications to clients, using serverless architecture based on AWS Lambda, SQS, and S3. Implemented an asynchronous processing pipeline for mass email sending, integrating Oracle Database, SQS, and SendGrid, allowing parallel notification processing and ensuring high system scalability. Developed services for secure JWT token generation and validation, including refresh token mechanisms and database-based validation to control access to sensitive information. Implemented automatic message processing from SQS queues to SendGrid, managing rate-limiting, automatic retries, and storing sent emails in S3 for auditing and traceability. Designed the email event tracking system using SendGrid webhooks, allowing registration of events such as deliveries, opens, clicks, and bounces for notification monitoring and analysis. Integrated dynamic HTML templates stored in S3, allowing personalized notification generation through variable replacement and automation of the sending process. Designed and developed REST APIs in ASP.NET Core to support vacation module operations, including period management, requests, and internal approval workflows. Implemented integration with Oracle Database using stored procedures and optimized queries, allowing more efficient execution of complex business operations. Analyzed and optimized SQL queries and stored procedures that generated unnecessary latencies, improving system throughput in concurrent operations. Implemented in-memory caching using IMemoryCache to store frequently consulted information, reducing repetitive database accesses and significantly improving service response times. Implemented integration between frontend and backend through decoupled REST APIs, facilitating system evolution and improving maintainability. Developed the frontend of the module using React, building a modern and responsive interface for managing vacation requests and viewing administrative periods.