Willian Cozzi Candido
Software Engineer · Full Stack · Brazil
About
Software Engineer with 5+ years of experience building scalable web and mobile applications, most of it in SaaS and high-volume systems, across front-end and full stack, working close to Product, Design and Engineering.
I started on the front end and grew into full stack, so I can take a feature end to end: the API, the data, the interface and the deploy. That range is what lets me make trade-offs with the whole picture in view.
AI is part of how I work now: agents, MCPs and spec-driven workflows, from planning to review. I look for the simplest solution that survives the volume, and for software the next person can pick up without a handover.
Stack
- Frontend: React, Next.js, TypeScript, React Native, Expo, Tailwind CSS
- Backend: Node.js, NestJS, Go, PHP, REST APIs, gRPC
- Data: PostgreSQL, MongoDB, DynamoDB, BigQuery, Supabase, Prisma
- Architecture: Monorepos, API design, Distributed systems, Event-driven design
- Developer experience: CLI tooling, OpenAPI, Storybook, MCP, Spec-driven development
- Testing: Jest, Vitest, Playwright, Testing Library
- Infrastructure: AWS, GCP, Docker, Kubernetes, CI/CD
- Observability: Grafana, Sentry
- Real-time: Webhooks, WebSockets, Push notifications
- AI: LLM integrations, Amazon Bedrock, Claude, Agents, Tool calling
Things I've built
- Built and evolved a high-volume checkout and payments platform, where the company transacts more than R$3 billion per year.
- Built fulfillment features on web and mobile, including a React Native app used on the warehouse floor.
- Built ADA, an AI support agent wired into engineering tooling, cutting the support tickets reaching the team by ~70%.
- Built the public Qive developer portal, with an interactive API playground.
- Built NFSe features on a fiscal platform that processes 3.8 billion documents a year.
- Co-founded and built polefy, a kart-track management platform with web, admin and mobile apps.
- Built and shipped Meu Feed Pronto, Tocha and Veil Abyss.
Interests
Education
Systems Analysis and Development at Catholic University of Brasília (UCB), graduated 2021.