A record nobody can edit behind your back
Each clock entry stores a SHA-256 hash of its content chained to the previous one. If someone edits the database by hand the chain breaks, and the panel shows exactly which link.
02 / 04Time-tracking SaaS
Gremial
Multi-tenant SaaS for Spanish time-tracking law. Two apps on the App Store and Google Play, tamper-proof audit trail.
- My role
- Design, code, native apps and deployment
- Year
- 2026
Stack
TurborepoExpoNode.jsPostgreSQLStripeVitest
- commits in 6 weeks
- 210
- apps in one monorepo
- 6
- test files
- 216
- apps in the stores
- 2
01The problem
Since 2019 every company in Spain must record each person's working hours and keep them for four years. The bar, the garage or the clinic with 3 to 40 staff is stuck between a spreadsheet that proves nothing and HR suites that need a consultant to roll out. Gremial is built so you sign up and have the team clocking in within ten minutes.
02What I built
- 01Turborepo monorepo: REST API, company panel, internal admin, public site and an Expo native app
- 02GPS geofence clock-in, a kiosk tablet with single-use QR codes, and offline mode that syncs later
- 03Double acceptance: every correction is a proposal from the company that the employee accepts
- 04Shift planner, absences, labour-agreement alerts and a monthly report in PDF, Excel and CSV
- 05Temporary read-only access for labour inspectors
- 06Stripe billing and a public demo that spins up a company per visitor and deletes it two hours later
03Decisions that matter
The company never corrects alone
Editing, creating or voiding an entry is a proposal with a reason that the employee has to accept. It protects the worker, and it's the employer's best defence in an inspection.
The server sets the time, and clocking in never blocks
No timestamp from the phone is ever trusted. And if the camera, GPS or signal fails, the entry is saved anyway and flagged as having no evidence: complying with the law can't depend on a sensor.
No data crosses companies
Postgres row-level security, every query through a client bound to the company, and one serializer per audience: no endpoint ever returns a raw row.
04In motion
✓
Entrada registrada · 08:00:12
Dentro de zona · 18 m
QR · 30s