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DevFlow Labs Case Studies

Public technical case studies from DevFlow Labs, a product engineering ecosystem focused on SaaS, automation, AI-assisted workflows, operational dashboards and reusable product architecture.

This repository works as the public portfolio layer for products and systems that may have private production code, protected business logic or internal deployment details.

What is DevFlow Labs?

DevFlow Labs is a product lab created by Gustavo Marques de Lima to design, build and document real-world digital products with a strong focus on:

  • SaaS architecture
  • Fullstack product engineering
  • AI-assisted workflows
  • Automation platforms
  • Multi-tenant systems
  • Privacy-first and local-first design
  • Billing, usage tracking and operational dashboards
  • Technical documentation as product strategy

Case Studies

Case Status Type Main Stack What this demonstrates
Investiga+ Public product / production-oriented SaaS Next.js, React, Node.js, Express, Prisma, PostgreSQL, Jest Secure auth, CNPJ intelligence, API integration, caching, history and SaaS foundation
ApplyFlow Public case study Local-first productivity product Chrome Extension concept, Next.js, TypeScript, local storage, OpenAI optional Privacy-first workflows, application tracking, candidate productivity and AI-assisted coaching
WhatsApp Platform Private product / public case Multi-tenant SaaS Next.js, TypeScript, Prisma, PostgreSQL, WhatsApp Cloud API, Stripe, OpenAI Multi-tenant architecture, webhooks, AI replies, billing, inbox operations and operational metrics
DevFlow Financeiro Private product / public case Financial SaaS Next.js, TypeScript, Prisma, PostgreSQL, Tailwind CSS Product score engine, dashboard UX, business rules, insights and monthly financial routines
Career Suite / ATS Tools Public case study AI-assisted career tooling Next.js, TypeScript, OpenAI API, local-first analysis Resume matching, job analysis, ATS-style scoring, interview preparation and privacy-aware AI
Vibe Intel Experimental lab AI/agents research TypeScript, Node.js, Fastify, PNPM, Turborepo Experimental AI agents, operational intelligence, modular packages and release automation
JWT Auth Public module Reusable backend module Node.js, Express, JWT, TypeScript Reusable authentication, middleware design, access control and package-oriented engineering

Repository Map

case-studies/
├── investiga-plus/
├── applyflow/
├── whatsapp-platform/
├── financeiro/
└── career-suite/

docs/
└── architecture/
    ├── ai-workflows.md
    ├── auth-and-rbac.md
    ├── billing-and-usage.md
    ├── local-first-products.md
    └── multi-tenant-saas.md

Architecture Notes

Document Topic
Multi-Tenant SaaS Architecture Tenant isolation, user roles, modular product boundaries and scalable SaaS foundations
Authentication and RBAC JWT, protected routes, role-based access and secure session handling
AI Workflows Human-in-the-loop AI, optional AI layers, structured output and automation safety
Billing and Usage Plan limits, usage aggregation, overage logic and Stripe-based SaaS monetization
Local-First Products Browser/local storage, privacy-first architecture, JSON handoff and user-owned data

Product Engineering Principles

Product-first architecture

Each product starts from a real workflow problem and is shaped around measurable user value, operational clarity and future monetization potential.

Modular fullstack engineering

Products are structured around clear boundaries between UI, domain logic, API layer, database, external integrations and operational concerns.

AI as an enhancer

AI is used to accelerate analysis, support decision-making and improve productivity. Core workflows remain understandable, testable and maintainable.

SaaS-ready foundations

Authentication, permissions, usage limits, billing, dashboards, observability and deployment concerns are treated as architecture decisions from the beginning.

Documentation as product

READMEs, case studies, ADRs, runbooks and roadmap notes are part of the product strategy, not an afterthought.

Public Repositories

Repository Purpose
devflow-modules/investiga-mais Public SaaS product and technical case
devflow-modules/jwt-auth Reusable authentication module
devflow-modules/applyflow-case-study ApplyFlow public case study
devflow-modules/devflow-case-studies Central public case study hub
devflow-modules/vibe-intel Experimental AI and operational intelligence lab

Private Production Monorepo

The production-oriented DevFlow Labs monorepo is private by design:

devflow-modules/devflow

It is used as the canonical internal source for apps, packages, architecture, product work, deployment strategy and operational documentation.

Public repositories in this organization expose selected products, reusable modules and technical case studies without exposing sensitive business logic or private implementation details.

Portfolio Value

This repository demonstrates:

  • Ability to design products from zero
  • Fullstack architecture maturity
  • SaaS and product engineering mindset
  • AI integration in real workflows
  • Multi-tenant and operational systems thinking
  • Technical storytelling and documentation
  • Ownership over product, roadmap and engineering delivery

Suggested Reading Order

  1. WhatsApp Platform — strongest SaaS architecture case
  2. Investiga+ — public SaaS and fullstack implementation
  3. ApplyFlow — local-first and privacy-first workflow product
  4. Career Suite — AI-assisted career tooling
  5. DevFlow Financeiro — dashboard, score engine and product insights

Roadmap

  • Add screenshots and GIFs for each product
  • Add architecture diagrams
  • Add decision records for key trade-offs
  • Add demo videos
  • Add bilingual versions of priority cases
  • Add public demo data where applicable
  • Add more detailed product metrics and roadmap notes

Author

Created by Gustavo Marques de Lima.