Jeferson – React, Node.js, Typescript

An AI-first platform for building custom reinforcement learning environments used to train advanced AI models.

• Deliver full features across frontend, backend, APIs, and databases in unfamiliar codebases, through review to customer delivery.
• Build typed end-to-end API flows with tRPC to keep frontend and backend contracts aligned.
• Resolve application and database bottlenecks through indexing, query tuning, storage optimization, and more efficient data loading.
• Own production incidents from reproduction and root-cause analysis to hotfix, deployment, and post-release validation.
• Act as the final quality gate before delivery: code review, exploratory testing, Playwright end-to-end tests, and Storybook component checks.
• Run parallel coding agents in Git worktrees and isolated environments, keeping responsibility for technical decisions and correctness.
• Improve CI, engineering guidelines, and agent instructions, and mentor teammates on them.

An AI-first SaaS product that lets businesses handle customer service and appointment scheduling through natural-language conversations.

• Took the product from MVP to production launch as the lead engineer.
• Built an LLM-powered engine that interprets user intent and coordinates tools and application workflows.
• Designed asynchronous, resilient message processing so customer messages are not lost and workflows are not interrupted.
• Added a corrective feedback loop to agent execution that detects invalid behavior and steers the next action.
• Combined application state, validation, recovery, and human handoff for cases that need intervention.
• Set up the AWS infrastructure and GraphQL data layer from scratch.
• Built RAG question answering over customer conversations, using retrieved message history and customer summaries.
• Implemented embedding-based contact search in PostgreSQL.

A web platform connecting professional and aspiring athletes with clubs, agents, scouts, and sponsors across the global sports industry.

• Modernized the platform after MVP, owning full-stack improvements, infrastructure, performance, and deployment automation.
• Migrated the JavaScript codebase to TypeScript, cutting runtime errors by catching type defects during development.
• Added Nginx and Amazon CloudFront caching so the platform could serve more concurrent users.
• Moved the platform between AWS accounts with no downtime, redesigning IAM roles, VPC connectivity, and resource organization.
• Containerized the stack with Docker on Amazon ECS with Fargate, with autoscaling on CPU and custom CloudWatch metrics.
• Set up GitHub Actions CI/CD for repeatable provisioning and releases.
• Built and maintained GraphQL APIs giving frontend clients a typed interface to platform data.

A SaaS platform that centralizes container import and shipment tracking, pulling shipment data from government portals and email into one place.

• Designed the platform and led its development.
• Automated shipment-data collection from government portals and email, removing manual checks across sources.
• Designed event-driven ingestion with DynamoDB Streams, Amazon SQS, and S3 triggers, with recovery from collection and sync failures.
• Built the application on Next.js and Amplify, connecting ingestion to shipment follow-up and container tracking screens.
• Made provisioning and deployments repeatable with Amplify and AWS CloudFormation.
• Centralized authentication and access control with Amazon Cognito.
• Led and mentored two junior developers through architecture guidance and code reviews.

A platform that helps musicians find gigs, connect with other musicians, and showcase their work.

• Owned full-stack web development of the platform.
• Designed a responsive interface for users on weak connections and low-end devices, guided by audience research.
• Improved loading and perceived speed with lazy loading, image placeholders, and loading skeletons.
• Implemented server-side rendering to support organic discoverability.
• Started the mobile migration from Flutter to React Native to share code across web and mobile.

High-scale, cloud-based creative SaaS platform that empowers marketers, designers, and agencies to create and publish no-code interactive digital experiences (e.g., animated infographics, microsites, landing pages, reports, and immersive content). Primary users are enterprise marketing teams and creative professionals at leading brands, who build engaging, responsive content that drives attention, engagement, and action across devices. Core functionality includes a drag-and-drop studio for real-time collaborative design, animation tools, analytics for engagement metrics, global CDN delivery, and integrations for seamless publishing and e-commerce.

• He boosted product performance, maintainability, and feature velocity by migrating legacy Backbone.js modules to modern React components, enhancing reliability and enabling faster development cycles across the platform.
• He significantly improved platform accessibility for enterprise clients by implementing comprehensive keyboard navigation and resolving screen-reader compatibility issues in auto-generated interactive content.
• He accelerated backend modernization as a core contributor to the NestJS microservices architecture, replacing outdated legacy services with scalable, message-driven APIs that supported higher loads and better separation of concerns.
• He raised engineering quality standards by enforcing ~100% API documentation coverage through TypeScript decorators combined with custom ESLint rules, ensuring consistent, self-documenting codebases.
• He reduced defects and increased release confidence by systematically introducing automated unit, integration, and end-to-end (E2E) tests across critical paths.
• He mentored engineers and elevated team productivity through detailed code reviews, architectural guidance, and establishment of contribution standards in a collaborative environment.
• He cut cloud and local development costs substantially by replacing VMWare-based environments with standardized Docker containers, streamlining developer setups and reducing infrastructure spend.
• He shortened deployment cycles by optimizing Jenkins pipelines and container build processes in the monorepo, improving overall delivery speed.
• He enabled scalable global content delivery by contributing to the migration from Fastly to Cloudflare CDN, including automated service configuration via Terraform for dynamic routing and policies.
• He maintained and optimized VCL logic for advanced caching, dynamic backend routing, and performance tuning to deliver faster site experiences.
• He validated horizontal scalability of the legacy ShareJS real-time collaboration layer through a successful proof-of-concept, providing critical guidance for future architectural decisions.

An early large-scale conversational AI tutoring platform powered by IBM Watson, designed for EdTech and corporate learning environments. Primary users included students, learners, educators, and corporate training programs. Core functionality centered on dialog-based interactions using natural language processing to deliver personalized, adaptive tutoring experiences that boosted engagement, learning personalization, and efficiency in educational and training scenarios.

• He contributed to one of the company's first large-scale AI initiatives by developing features for an IBM Watson-powered dialog-based tutoring system, boosting student engagement, personalization, and product differentiation through conversational AI interactions.
• As part of the CI/CD team, he prepared the infrastructure structure and pipelines to reliably run and deploy the tutoring system on AWS, enabling scalable cloud operations and consistent releases for the AI-driven EdTech product.
• He achieved substantial reductions in infrastructure costs through resource consolidation and shared-instance models.

An enterprise HR platform was a legacy system built on Adobe Flex, serving large organizations, HR teams, and enterprise environments for managing core HR processes such as employee lifecycle, onboarding, performance management, and compliance workflows. The project focused on modernizing this legacy application into a contemporary web-based architecture to achieve superior performance, maintainability, scalability, and long-term viability in high-volume enterprise HR settings.

• He led a critical application modernization effort by migrating legacy HR platform from Adobe Flex to AngularJS, significantly improving maintainability, performance, development velocity, and long-term supportability for enterprise HR processes.
• He supported architecture decisions, code quality, and maintainability through in-depth performance reviews, design guidance, and implementation of best-practice patterns that enhanced readability and reduced technical debt.
• He improved software reliability, reducing costs, and streamlining development, adding a solid test strategy.

Leading Brazilian digital entertainment and gaming company that published and operated high-traffic online games (including MMORPGs like Ragnarok Online), managed e-commerce for digital goods, community forums, and supporting web platforms serving millions of users across LATAM. Primary users were gamers, community members, content teams, and internal operations staff. Core functionality included scalable web/e-commerce frontends, content management systems (CMS), real-time game integrations, billing/payment gateways, large-file delivery, behavioral tracking for marketing insights, and robust infrastructure for performance under heavy load.

• He led the development of core web and e-commerce platforms, delivering new features and modernizing legacy systems with PHP, .NET Framework, AngularJS, and Yii frameworks, which greatly improved stability, user experience, and scalability for millions of daily active users.
• He designed and built scalable CMS and internal tools that dramatically reduced manual workload for content teams and accelerated time-to-publish for game updates, promotions, and community content.
• He enhanced system performance and reliability by optimizing Nginx/Varnish configurations, implementing advanced cache strategies, and tuning backend services across multiple high-traffic applications.
• He modernized authentication flows by integrating secure ASP.NET MVC token-based services with PHP applications, boosting overall security, seamless cross-product login experiences, and user trust.
• He reduced operational overhead by developing custom dashboards, monitoring tools, and incident-response integrations that provided real-time visibility into system health and significantly sped up troubleshooting and recovery.
• He streamlined development workflows by implementing continuous integration with Jenkins and enabling blue-green deployments, allowing safer, faster, and more frequent releases with minimal risk.
• He executed critical migrations, including shifting the community forum from C# to vBulletin and upgrading multiple legacy systems, all completed with minimal downtime and no major disruptions to users.
• He built data and behavioral tracking APIs that empowered marketing and product teams to collect actionable insights, optimize campaigns, and drive better user retention and monetization.
• He elevated developer productivity and code quality by mentoring team members on SOLID principles, best practices, and test-driven development, fostering a stronger engineering culture.
• He supported mission-critical systems such as billing, payment gateways, and large-file delivery tools, ensuring high performance, reliability, and uptime during peak high-volume operations.