I build production-oriented SaaS products, automation platforms, APIs, dashboards and AI-assisted workflows with a strong focus on architecture, security, usability and business impact.

Portfolio • DevFlow Labs GitHub • Case Studies • LinkedIn • Email

If you are a recruiter, hiring manager or technical interviewer, review these first:

Some products are private because they contain proprietary workflows, business logic, credentials, client-related architecture or deployment details. For those, I maintain public case studies and documentation with product context, architecture, decisions, screenshots and roadmap.

I am a Fullstack Product Engineer based in Santos, São Paulo, Brazil, focused on building complete digital products — from product strategy and architecture to implementation, testing, documentation and deployment.

My strongest work is organized under DevFlow Labs, a product engineering ecosystem focused on SaaS platforms, automation, AI-assisted productivity and business tools.

Best fit roles: Fullstack Engineer, Product Engineer, Senior Frontend Engineer, SaaS Engineer, Automation Engineer, AI Workflow Engineer.

Repository: https://github.com/devflow-modules/investiga-mais
Live: https://investigamais.com

SaaS platform for CNPJ/company intelligence and business data analysis.

Why it matters:

• Fullstack SaaS delivery
• Secure authentication with JWT + HttpOnly Cookies
• CNPJ lookup with external API integration
• Local cache strategy for repeated searches
• User-scoped search history
• Modular backend architecture
• Automated tests with Jest
• Docker and CI/CD-ready structure

Best for evaluating: fullstack delivery, authentication, API integration, data modeling, testing and product thinking.

Public Case Study: https://github.com/devflow-modules/devflow-case-studies/tree/main/case-studies/whatsapp-platform
Case Hub: https://github.com/devflow-modules/devflow-case-studies

SaaS/white-label WhatsApp operations platform built inside the DevFlow ecosystem with Next.js, TypeScript, Prisma, PostgreSQL, Stripe and WhatsApp workflow modules.

Why it matters:

• SaaS and white-label product architecture
• WhatsApp operations and onboarding workflow
• Tenant configuration and API key generation
• JWT authentication with cookies
• Stripe billing and webhook handling
• Metrics dashboards, agents, queues, FAQ, feedback and exports
• Accessibility checks with Playwright + axe

Best for evaluating: product engineering, SaaS architecture, operational dashboards, billing integration, auth flows and business-focused automation.

Case Study: https://github.com/devflow-modules/applyflow-case-study
Ecosystem Repository: https://github.com/devflow-modules/devflow

Local-first and privacy-first workflow assistant for job applications, candidate productivity and interview preparation.

Why it matters:

• Local-first product architecture
• Privacy-first candidate workflow
• Human-in-the-loop automation design
• Chrome Extension MV3 + Next.js dashboard concept
• JSON import/export portability
• Optional AI coaching with user-controlled API key
• Documentation-driven product communication

Best for evaluating: product architecture, frontend/dashboard thinking, local-first software design, AI-assisted workflows and documentation quality.

Repository: https://github.com/devflow-modules/jwt-auth

Reusable JWT authentication module for Node.js applications.

Why it matters:

• Access token and refresh token support
• Password hashing and verification
• Express route protection middleware
• Role-based authorization middleware
• HttpOnly Cookie support
• CI, Codecov, npm badge and test coverage

Best for evaluating: reusable package engineering, authentication fundamentals, API design and testing discipline.

GitHub Organization: https://github.com/devflow-modules
Portfolio: https://devflowlabs.com.br
Case Studies: https://github.com/devflow-modules/devflow-case-studies

DevFlow Labs is my product engineering lab for building and documenting SaaS products, automation platforms, AI-assisted workflows and reusable modules.

Engineering focus:

• Fullstack SaaS architecture
• Multi-tenant systems
• Secure authentication and authorization
• API integrations and webhooks
• AI-assisted product workflows
• Dashboards and operational tools
• Testing, CI/CD and technical documentation

React.js • Next.js • TypeScript • JavaScript • Tailwind CSS • Chakra UI • ShadCN UI • Styled Components • HTML5 • CSS3 • Framer Motion

Node.js • Express.js • Python • FastAPI • Prisma ORM • REST APIs • Webhooks • JWT • Cookies HttpOnly • Authentication & Authorization

PostgreSQL • SQLite • Supabase • Redis • Docker • Vercel • Railway • Render • GitHub Actions • CI/CD

Jest • Vitest • Playwright • Selenium • Testing Library • Pytest • RPA • API testing • E2E validation

OpenAI API • WhatsApp Cloud API • Stripe • ReceitaWS • Webhooks • CRM integrations • Automation workflows

• Building scalable SaaS products under DevFlow Labs
• Improving AI-assisted product workflows
• Strengthening fullstack architecture with Next.js, React, Node.js and TypeScript
• Creating automation and productivity tools with real business use cases
• Growing as a Fullstack/Product Engineer for remote and international opportunities

• LinkedIn: https://www.linkedin.com/in/gustavo-marques-00
• GitHub: https://github.com/gustavomarques00
• DevFlow Labs GitHub: https://github.com/devflow-modules
• Portfolio: https://devflowlabs.com.br
• Email: gustavomarquesmm@gmail.com