Available for new projects
Front, back and infra.
I build complete applications in Next.js and TypeScript: data modelling, API, role-based authentication and deployment. From landing pages to multi-tenant SaaS running in production.
01What I do
I build complete products: data modelling, API, permission rules, deployment and the interface the user sees. Every layer designed together with the others.
Interfaces in Next.js and React, typed end to end with TypeScript.
Route Handlers and Node.js, with input validated by Zod. Python when the problem calls for it.
Firestore and PostgreSQL, modelled around who uses it, what they need and who may see what.
Role-based permissions enforced on the server — in Security Rules and RLS — not hidden in the interface.
Multi-tenant with real isolation between customers, and routines that run on their own as cron jobs.
Vercel and GitHub Actions: from repository to production with no manual step in between.
In production
Scroll to see the products running.
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MHL.dev
Digital products, from database to deployment.
Now, one by one.
02Selected work
Products built end to end — from multi-tenant SaaS to client landing pages.
A complete product, from database to deployment: each firm is a tenant isolated in Firestore, with per-role permissions enforced in the Security Rules — not in the interface. It pulls court notices from the Brazilian national judicial gazette by bar registration number, every business day, on its own.
Four modules that would normally be four separate apps: habits with levels and coins, a focus timer, expense tracking and a personal library. Local state that syncs to Firestore when a session exists, so it works offline and carries over to another device.
Sites and stores
Jewellery landing page that converts straight into WhatsApp.
E-commerce · Jewellery
HTML · CSS · JavaScript
Portfolio split by style, with booking through WhatsApp.
Brand site · Tattoo
Next.js · Tailwind CSS
A restrained brand site for a law firm.
Brand site · Law
HTML · CSS · JavaScript
Limited-edition store with a cart that closes on WhatsApp.
E-commerce · Fashion
Next.js · Tailwind CSS
03Case studies
The decisions that don't show up on screen — and why they were made.
Case 01SaaS · Multi-tenant2026
Solo project — product, architecture, back-end, front-end and deployment
Problem
A small law firm runs its caseload on spreadsheets and WhatsApp. The workflow exists in people's heads — intake, calculation, filing, hearing, settlement — but nobody can see where a given case is, and a court notice only surfaces when someone remembers to check the official gazette. AdvBoard puts that workflow on a screen and fetches the notices without being asked.
Solution
Multi-tenant SaaS for Brazilian labour law firms: case flow on a kanban board, a calendar derived from the cases themselves, and court notices fetched automatically every business day.
Technical decisions
By the numbers
8
Workflow stages
9
API routes
2
Official data sources
154
Lines of Security Rules
Technologies
Case 02App · Productivity2026
Solo project — product, front-end and back-end
Problem
Four things that normally live in four different apps: habits, focus, money and reading. Switching apps all day is enough friction to abandon all four. Lume puts them behind one interface, with a dashboard that answers the question that matters in the morning: what do I do now.
Solution
Personal assistant with gamified habits, a focus timer, expense tracking and a library — local state that syncs to Firestore when a session exists.
Technical decisions
By the numbers
4
Modules
100%
Works offline
Technologies
04Stack
The technologies behind the projects above, organised by layer.
Matheus Henrique
MHL.dev
Maceió, AL
05About
I'm a full stack developer based in Maceió, Brazil. I build entire products — data modelling, API, permission rules, deployment and the interface the user sees. I don't ship pretty screens wired to nothing.
My process starts with the business: who uses it, what they need, and who is allowed to see what. The architecture follows from that — the code comes after.
Where I work
06Process
It starts with the business, not the code. The architecture comes out of understanding — and the code comes after it.
01
Who uses it, what they need and who may see what. That is where the architecture comes from.
02
Data modelling, API contracts validated with Zod, and permission rules designed for the server to enforce.
03
Next.js and strict TypeScript, from the API route to the component the user touches.
04
Tests with Vitest and security rules tested in the emulator: a wrong permission doesn't show on screen, it shows up as a leak.
05
Vercel and GitHub Actions, with cron jobs for whatever has to run on its own every day.
07By the numbers
mhl.dev / by the numbers
6 documented here
"strict": true
08Contact
Need a system built from scratch, an API for an app that already exists, or someone to own the product end to end? Get in touch — I reply fast.
Straight to WhatsApp