Lucas
Duarte
>Senior Full-stack Developer
React and Node.js day to day — and, in recent years, systems with agentic AI: agents, LLMs and MCP.
About
Full-stack end to end: interfaces in React, APIs in Node.js and systems with agentic AI.
I work with TypeScript from end to end, favouring simple architecture and code other people can maintain.
Stack
- react
- next.js
- typescript
- node.js
- python
- agentic ai · mcp
Recent projects
Experience
- Apr 2025 — Jul 2026
Forecastr
Senior Software EngineerTechnical reference for the proprietary financial calculation engine.
- Loading large volumes of financial data took ~12s; with caching, query optimisation and changes to how data was processed and accessed, it dropped to under 2.5s.
- Some interactions took ~2,500ms and stalled analysis; by restructuring the processing behind them, they came down to ~200ms.
- Operations over batches of ~240k records blocked the app; I moved the work into pipelines with job workers and streams, making reads, writes and processing efficient without blocking the main application.
- Reliability depended on manual checking; I built a unit, integration and end-to-end test suite, and bug reports in the covered areas fell by around 80%.
- Investigating bugs ate hours of the team's time; I built an MCP server and AI agents with n8n and GitHub Actions that reproduce the report, generate Playwright tests and verify the fix, leaving the developer the technical call and the final review.
reactnode.jstypescriptnest.jsplaywrightmcpn8ngithub actions - Apr 2024 — Apr 2025
MaisTODOS
Senior Software EngineerPlatform integrated with the company's financial products.
- The company had no platform bringing its financial products together; I built the first version and took part in the backend architecture decisions on Node.js and AWS and in the integration with internal services.
- Access had to be unified and secure across products; I maintained and evolved the authentication and authorisation architecture on AWS Cognito, including the company's SSO.
- A multi-module system tends to couple and stall; I applied Clean Architecture and SOLID alongside a broad testing strategy, reaching 100% coverage and making the application safe to maintain and evolve.
- Integrations with external services were significantly slow; I added Redis caching and cut the response time's dependency on repeated third-party calls.
- The products shared no visual language; I worked on the company's Design System, both building the reusable components and on the UI and UX decisions.
reactnode.jstypescriptnest.jspythonawsaws cognitoredis - Mar 2022 — Apr 2024
DASA
Senior Software EngineerTelemedicine at Latin America's largest diagnostics company.
- The main telemedicine application needed to move on; I took part in its redesign, working on both the user experience and the frontend architecture.
- Legacy code produced recurring bugs and made every change risky; I added unit test coverage over it and led its refactoring with Adapter, Facade and Factory, bringing the failure rate down.
- The monolithic frontend made parallel work across teams hard; I structured a modular micro-frontend architecture with Webpack Module Federation, letting parts evolve independently.
- The Jenkins CI/CD pipeline was slow and held deliveries back; I introduced parallelism and cut the time of each run.
- Poorly sized queries degraded production performance; I acted as the MongoDB technical reference, monitoring and optimising queries, while integrating video through Twilio and Zoom and mentoring junior developers.
reactnode.jstypescriptnest.jswebpackmodule federationmongodbjenkinstwilio sdkzoom sdkmachine learning - Aug 2021 — Feb 2022
BOTY
Senior Software EngineerDigital products across the Wevy group.
- Every product reimplemented its own components; I built the company's proprietary Design System with Atomic Design, standardising the visual identity and speeding the teams up.
- Real-time communication had to serve several Wevy group products at once; I implemented an architecture over the XMPP protocol focused on performance and able to hold a large volume of connections.
- Manual processes ate the clients' time; I worked on a chatbot with Machine Learning features, available inside the platform and externally through an SDK.
- There was no foundation for shipping and distributing the products; I set up CI/CD on Google Cloud Platform, Firebase authentication, Cloud Storage integration, a GraphQL API and a video player SDK.
reactnode.jstypescriptgraphqlxmppfirebasegcpmachine learning - Aug 2020 — Aug 2021
PECEGE
Software EngineerPlatform for managing the thesis-advising process.
- The project was close to its deadline, unlaunched and at real risk of slipping; I helped the team prioritise what had to exist to ship, and the platform went live on time — it is still running today.
- Advisor–student conversation depended on email and a previous chat that was expensive to run on servers and a relational database; I led a real-time chat built from scratch on Firebase and Cloud Functions, cutting cost by around 50% and getting adopted by other teams.
- Students wrote and reviewed their work outside the system; I built the collaborative experience inside the platform, with a WYSIWYG editor, content reviews and large document uploads.
- Assigning advisors to students by hand did not scale; I built a .NET Core API with a statistical algorithm that ranks and matches by thesis topic, reaching around 70% accuracy.
- The frontend failed basic accessibility criteria; I refactored the interface with that focus and reached 100% on the criteria assessed by Google Lighthouse.
reactnode.jstypescriptfirebasegcp.net coremachine learninglighthouse - Aug 2017 — Aug 2020
Intelup
Software EngineerShop-floor digitalisation with Industry 4.0 technologies.
- The AngularJS frontend piled up sync bugs from heavy two-way data binding, on an already deprecated technology; I proposed and led the gradual migration to React, rendering components inside the legacy app, finished in about a year and leaving some pages up to 5x faster.
- The migration proposal was not approved right away; I built an internal B2B subscription and billing application from scratch in AdonisJS, React and Redux, with an MVP in about two months, which served as proof and unblocked the migration of the main app.
- The on-premise rollout required manual setup and took over three days at clients with limited internet; I automated it with Docker and an offline installer for Windows and Linux, bringing the environment up in about three hours.
- Industrial environments with unstable connectivity could not depend on immediate syncing; I built an Electron application with a Node.js OPC service that collects millions of points locally and queues them to sync into InfluxDB once a connection is available.
- Companies wanted to compare indicators without exposing their identity; I implemented the authentication and anonymisation strategy of a cross-company benchmarking service, with random keys kept stable within the analysed period and rotated when the window changes, preserving report consistency and LGPD requirements.
reactnode.jsreduxreact nativeangularjsadonisjselectronweb workerspythonpandassqlalchemypostgresqlinfluxdbdockerawsopc
Blog
Let's talk?
Open to projects and full-time opportunities. Reach out on WhatsApp or by email.