Available for projects and roles
Senior Full Stack Engineer · Buenos Aires, Argentina
I build fast, secure products for fintech, security and the web.
01About
Eight years shipping software, from Mercado Pago's payment tools to Pomelo's fintech platform and Strike's offensive-security products.
I work across the whole stack: React and React Native on the front, Node services and Postgres behind them, and the infrastructure that keeps it all running.
I care about systems that stay fast, observable and secure as they grow. Today I build my own products and take on a few projects at a time.
02Experience
2025 – 2026
Offensive security
Led full-stack work at a cybersecurity company focused on continuous pentesting: security-first platforms, threat-intelligence flows and high-performance services.
2022 – 2024
Fintech infrastructure
Built and ran critical fintech applications with React, Next.js, Node, NestJS and GraphQL. Promoted to senior to lead technical initiatives and mentor developers.
2017 – 2022
Payments · Mercado Libre
Went from customer experience to software development. Led payment-integration tools with React, Node and MySQL, with monitoring on Datadog, Kibana and New Relic.
Education
University Technical Degree in Corporate Security
Universidad Kennedy · In progress · Mar 2026 – Jun 2028
Certification
AWS Well-Architected Best Practices
Amazon Web Services · 2023
03Selected work
01 / 07
Real-time PvP strategy game: Tribal Wars-style conquest with Argentine political satire.
An authoritative Fastify + Socket.IO game server, a procedurally generated world drawn as a PostGIS Voronoi map with deck.gl vector tiles, BullMQ workers and four payment providers. On the web, App Store and Google Play.
02 / 07
Detective logic puzzles: read the clues, catch the jewel thief.
A Next.js web app and an Expo app that draws the board with Skia + Reanimated, on a Hono + Zod serverless API with in-app purchases, Mercado Pago and ads.
MiPortalUK Académico
Linux · macOS03 / 07
Universidad Kennedy's Silverlight apps, running again on Linux and macOS.
Silverlight was discontinued in 2021 and the university's viewer only runs on Windows. I built Plata, an open-source Silverlight player on OpenSilver and WebAssembly: it reads the original .xap, adapts its assemblies to modern .NET and runs it in a tabbed desktop app, with a network gatekeeper that enforces Silverlight's access policies. Signed and notarized for macOS.
Unofficial and open source, built with the university's authorization.
04 / 07
The global platform for the polo community.
Player directory filtered by handicap, rank, country and club, a services marketplace, news, realtime community chat and surveys with reward credits. Bilingual, on a tRPC + Hono API.
05 / 07
A score keeper for any game, on iOS and Android.
Scores, history and player stats across game formats. Built with React Native and Expo, and published on the App Store and Google Play.
06 / 07
Automatic course enrollment for SIU Guaraní: 28 universities, 148+ programs.
A sub-minute cron that races credentials in parallel, AES-256-GCM encryption at rest, exponential backoff with Cloudflare and captcha detection, and jittered staggering to stay under rate limits.
07 / 07Client project
Premium website for a Patagonian construction company with 30+ years of history.
Showcases its developments in the Alto Valle of Río Negro and Neuquén, near Vaca Muerta, with aerial footage, 3D renders, smooth animations and a bilingual site.
04How I build
Authoritative servers, websockets, queues and workers that hold up under load.
Mercado Pago, Paddle, RevenueCat and crypto, with webhooks that never lose an event.
Encryption at rest, rate limits and secret scoping, from a background in offensive security.
Sentry, Datadog and OpenTelemetry, audit logs, retries and backoff: systems you can see into.
05Contact
Write to me. I usually answer within a day.
juanii.veltri@gmail.com