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Case studies
Case studies with the problem, my role, constraints, decisions and their costs, verified results and a security angle.
Featured
A study platform with payments, access control and timed exams
My own product: a sales site, a student app and an operations panel, three apps in one monorepo. The rules that touch money, access and personal data live on the server, in packages the three share, tested against a real Postgres. It is live and in commercial pre-launch; this case is about the engineering, not traction.
open the demo (A study platform with payments, access control and timed exams)
A security review of the business logic of my own system
I reviewed the business logic of my own system, with payments, credits, rankings and paid content, and fixed thirteen classes of flaws, each with a regression test. The process was an adversarial review that never touched production: every hypothesis reproduced in a failing test and fixed at the narrowest boundary. The costliest flaws were the ones scanners and generic checklists miss.
A multi-company onboarding platform with isolation in the database
Two companies of a business group use the same platform to onboard new hires, in the same database, without either one seeing a single row of the other's data. Each person gets a guided trail by phase, assembled for their department, role and contract, and the admin panel follows progress in real time without sending any personal data over the real-time channel.
open the demo (A multi-company onboarding platform with isolation in the database)
This site
A portfolio that works like a terminal session: every page answers a command, and the next commands are links, so anyone can navigate by clicking. People who prefer typing get a real terminal and a command palette, and all the content reads without JavaScript. The site itself is the evidence: its HTML, headers and commands can be checked in the browser.
A corporate site and an in-house CRM at the edge, with privacy as a requirement
A B2B group replaced an off-the-shelf CRM with its own system: a site in three languages that captures contacts through an interactive assessment and meeting booking, and a CRM with leads, a deal pipeline, a meeting queue, content and analytics. It all runs in a single Worker at the edge, with five access roles, owner-scoped data and Brazil's data protection law (LGPD) treated as part of the product.
open the demo (A corporate site and an in-house CRM at the edge, with privacy as a requirement)
A national confederation's member system, modernized with the legacy still live
A national professional confederation keeps its members' records, the digital membership card with a QR code, the regional offices' request batches and online membership with a contract and consent in a legacy PHP system that runs in production. As the sole engineer, I lead the modernization from the inside without stopping the system: version control, recorded decisions, tests from zero, CI with disposable databases and deploys with backup and automatic rollback.
open the demo (A national confederation's member system, modernized with the legacy still live)
Archive
The other case studies, one line each. Each one opens the full case.
- Exam intelligence that shows its math
My own internal tool for deciding which civil-service exam is worth producing material for: it ranks exams by a score made of five parts, extracts each exam board's pattern from past exams and estimates what is likely to be asked, always with the math written next to the number.
- A product and project management office, with concurrent editing and no lost work
An internal system to manage product, projects and people: Scrum and Kanban with sprints, a prioritized backlog, burndown and velocity, workload per person, a dossier for each project, a mind map and an executive view.
open the demo (A product and project management office, with concurrent editing and no lost work)
- A creative holding's website with an admin panel, secret-link proposals and invoices
The three-language website of a creative holding and the internal panel behind it: diagnosis requests, audience measured without cookies, SEO per page and language, accounts with roles and an audit trail.
open the demo (A creative holding's website with an admin panel, secret-link proposals and invoices)
- A factory of technical hiring challenges, with a live defense and a human decision
An internal tool that creates technical hiring challenges for 22 tracks at 4 levels, from intern to senior.
open the demo (A factory of technical hiring challenges, with a live defense and a human decision)
- A leadership cockpit for a product and technology director
A personal prototype that turns the scope of a product and technology director role into a management tool: the mandate and KPIs with targets, the decisions only that role can unblock, the systems inventory, a Scrum board, a leadership guide, meeting scripts, a proposal generator and a presentation builder.
open the demo (A leadership cockpit for a product and technology director)
- A question pipeline with style measurement and an acceptance gate
My own command-line tools and scheduled routines that measure how an exam board writes, check every batch of questions against that measurement and deliver only drafts to the study platform's panel, where a person approves or discards them.
open the demo (A question pipeline with style measurement and an acceptance gate)
- A luxury vehicle and asset registry, from editorial site to sales console
Two generations of a product for an international client in the luxury sector: an editorial register with its own CMS, two-factor login and cookieless audience measurement, then a vehicle storefront with a console for the sales desk.
open the demo (A luxury vehicle and asset registry, from editorial site to sales console)
- A high-end tourism portal prototype, with a data contract ready for the back end
A clickable, front-end-only prototype with fictional data of a high-end tourism portal for a lake region in inland Brazil, shown to a client.
open the demo (A high-end tourism portal prototype, with a data contract ready for the back end)
- Reviewing and modernizing a live event-control system
A PHP web system runs in-person events: attendees, check-in with a printed badge, support staff, booth sales with receipts and stock per event.
open the demo (Reviewing and modernizing a live event-control system)
- Media Archive: a catalog and personal list of films, series and anime
A personal prototype built in one night: a catalog that searches films, series and anime across four public metadata sources at once, shows each title's page, official trailers and where to watch legally, and keeps each person's list with a magic-link sign-in.
open the demo (Media Archive: a catalog and personal list of films, series and anime)