Stewart Charles

Led the migration of the tenant portal from a legacy web stack to an Expo-based React Native application, including establishing code review standards and testing protocols for the mobile team. Led migration of the property management platform to React Native and Expo, unifying iOS and Android client codebases into a single shared repository. Built secure REST APIs using Express and PostgreSQL to manage complex tenant billing cycles with multi-currency calculations and automated invoice generation workflows. Introduced TDD and Jest suites across frontend and backend teams, optimized PostgreSQL reporting performance with composite indexes and query rewrites, and mentored junior engineers through weekly code reviews and pair programming. Designed and built high-throughput backend services using Node.js and Nest.js on AWS EC2, and reviewed PRs across three engineering squads while standardizing TypeScript linting rules.

Developed patient engagement features in React Native and Expo, enabling healthcare administrators to send targeted appointment reminders and health surveys via mobile push notifications. Migrated legacy MySQL schemas to PostgreSQL, defining new relational models for patient records and ensuring data integrity with constraint validation and migration scripts. Built backend services with Node.js and Express for clinical data storage. Implemented background job processors using Node.js and Redis queues for bulk email dispatches to decouple sending from the main application thread. Created internal developer tools to validate API contracts against Swagger definitions. Implemented CI/CD pipelines with AWS CodePipeline and Docker to automate build verification and staging deployments. Resolved patient portal latency issues by adding Redis caching for frequently accessed provider directories.

Developed automated test suites for a mobile application using Expo and Jest, covering user authentication flows, appointment scheduling logic, and notification handling. Wrote integration tests using Selenium and Node.js to verify login flows and form submissions for the student registration system before releases. Designed REST API integration tests with Express and Axios to validate data consistency between an Expo client and backend Nest.js services. Built backend endpoints in Express and PostgreSQL to support faculty grading workflows. Implemented PostgreSQL and MySQL migration scripts and verification queries to ensure schema integrity during deployments and rollbacks.