Nicolás Yusta

Eleven sections on their own database: numbered quotes with PDF output, delivery notes reconciled against the quote, staged work orders and stock deducted on delivery. A quote that took hours now takes minutes, and the workshop was using it 15 days after signing. It runs 1,000 suppliers, 136 quotes and 113 delivery notes. A job-sheet parser took over 540 hours of labor previously added up by hand, and an integrity check I wrote surfaced two approved quotes with no sale on record. 72 days in, the client signed a second contract.

Vanilla HTML, CSS and JavaScript, no framework, no build step · multi-tenant Firestore · Vercel · CSP, HSTS, append-only audit log

Installable mobile app for taking payments at the front desk: 232 members, due dates, cash register and 401 payments, each with its author recorded. In a later support review I closed 34 code-injection points and fixed a backup that had been failing silently for six days. The client came back with seven paid changes, shipped with 54 automated tests.

Single-file PWA · Firebase with offline persistence · Google OAuth · Sentry

Tracked deliveries, courier settlements, per-client accounts and digital delivery orders signed on the courier's phone: 1,656 deliveries across 3,680 documents, growing by about 3,000 documents a month. The owner now closes in five minutes a settlement that used to take her a whole morning. I found and closed a data leak: the public HTML was serving 27 companies with emails and tax IDs because the login screen was a CSS overlay, not a real gate.

Vanilla JavaScript · Firestore · live map

The highest-volume one: 20,218 documents and 13,052 payments. A full-time employee used to copy payments onto paper index cards; today the owner enters four collectors' payments in under ten minutes a day. A 26-test data audit I wrote found 25 loans overcharged by ARS 465,500 and reported them without modifying a single record.

Vanilla JavaScript · Firebase · Chart.js