Results
Every number here has a source, and none is an estimate. Most of the cases come from the work of Kayo Souza, the tech lead of Kaizen Forge, told by him in the first person; the ones marked "via our studio" came through koy.haus or Haus. When a client is under NDA, we describe the industry and never invent the result.
by Kayo Souza, tech lead
Nike
Global marketing
I built the Asset Library behind 16M+ digital assets as sole engineer, and AutoCrop, a GenAI service that generates format-optimized crops and cut designers' prep time 44%, from 6.4h to 3.6h. I also automated marketing asset generation from Figma AutoLayout with correct typography.
by Kayo Souza, tech lead
Experity
Healthcare
Experity holds half of the US telemedicine market. I'm Tech Lead of the nearshore team on Care Agent, its LLM patient engagement and telehealth product. Appointment booking runs in code instead of the LLM, session telemetry keeps PHI out of every event, and the agent runtimes run under a 99.99% availability SLO with a canary every 5 minutes.
by Kayo Souza, tech lead
Yooga
Fintech · Restaurants
I led payments, with a team of 5 engineers, at a restaurant operating system with 7,000+ restaurants: Pix, Apple Pay, Google Pay and cards, a Kafka event layer, and the idempotent flows and signed webhooks that removed duplicate charges.
by Kayo Souza, tech lead
Yooga · SmartPOS
Fintech · Payment terminals
I architected and built SmartPOS, which runs Yooga natively inside payment terminals and integrates the terminal's payments: a Kotlin/Android app on Sunmi, Positivo and Tectoy devices with the Stone SDK.
by Kayo Souza, tech lead
Topo Contábil
Co-founded SaaS · Accounting
I co-founded Topo with an accountant: a modular platform that runs the accounting operation of multi-company groups on top of their ERP. I built the product architecture, engineering and security: row-level security forced on all 120 tenant tables, an assistant on Claude that answers with citations, and a versioned public API with a read-only MCP connector.
via our studio
Grupo EL
GovTech · Public sector
We contribute to the EL Produções ecosystem and its subsidiaries (Sapitur, Geocamp, Georastreamento, Elonline): public management, telemetry and tracking across 9 states, through koy.haus, our software studio.
via our studio
Startup (NDA)
Rescue · Product
A product a big agency had been building for 2 years without shipping. We stepped in through Haus, our MVP studio: in 30 days the backend was refactored, the UI redesigned and the product went live, ready for pitch and fundraising.
by Kayo Souza, tech lead
Brasa Cargas
Marketplace · Logistics
I founded a freight marketplace where freight agents post loads and truck drivers find them, with WhatsApp-first acquisition, public discovery and subscriptions through Stripe.
by Kayo Souza, tech lead
ReurBR
GovTech · Land regularization
I built ReurBR at Tegrus, where I worked from January 2019 to August 2020. There are two apps: a Vue 2 web app for the teams on each land-regularization project and a React Native app for field registration, which collects documents even without internet. The platform issues titles and certificates in templates ready for the registry office. Most of the deeds came after I left Tegrus; the figures below are the ones the ReurBR site publishes today.
by Kayo Souza, tech lead
TJ-ES
Public sector · Justice
I'm a software engineer, on a research grant, in Innovation in the Service of Justice, the modernization project of the Tribunal de Justiça do Espírito Santo, and I work across all of its tracks, taking care of the design system and the architecture standards for the court's 20 modernization projects. In the Engineering track I build works and contracts management, in Flask and Vue, with Clean Architecture checked by tests.
by Kayo Souza, tech lead
Accounting office
Automation · Freight
An accounting office checks the CT-e, Brazil's electronic freight invoices, of its trucking clients by hand every month, and one of the sources is the portal of a large logistics operation. I built a proof of concept in Python and Playwright: a read-only connector logs into the portal, downloads the report and the XML batch and answers, document by document, OK, DIVERGENT or NOT CHECKED. It became an end-to-end pilot, still in progress.
by Kayo Souza, tech lead
Sigil Protocol
Open source · AI agents
Open identity protocol for AI agents: an ID derived from an Ed25519 key, a signed agent document, a soul hash against tampering, signed interaction receipts, and key rotation and revocation. I wrote the spec and the TypeScript reference implementation, under the MIT license. The spec is still a draft.
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