Field operations . GST billing . Mobile
Time and Me
Authentication and repair billing for a watch service business
- authentication live
- Multi-labauthentication live
- billing since Jun 2026
- GSTbilling since Jun 2026
- first capture
- Offlinefirst capture
Status. In production. Authentication running across multiple fulfilment centre labs.
What it is
The authentication and billing systems behind a watch studio's two businesses. One side grades watches for a global marketplace's fulfilment centre labs, every watch logged before it can be listed or returned. The other runs the studio's repair shop on job cards and GST invoicing.
A spreadsheet workflow replaced by a mobile app for warehouse technicians and a web admin for operations managers, plus a separate job card and billing module.
The problem
Authentication labs across several fulfilment centres ran on spreadsheets: data loss risk, no audit trail, no visibility into throughput.
The warehouse floor adds its own constraints: unreliable wifi, shared Android devices, multi-language teams, and no tolerance for the app going down mid-shift.
What we built
A 12-screen offline-first technician app: login, item lookup, barcode scan, authenticity decision, component grading, photo capture, and a shift dashboard, all working without network and syncing once reachable.
An offline sync engine with a pending, syncing, synced, and failed state machine, and a batch endpoint that deduplicates on retry.
A two-step photo pipeline: the phone compresses and uploads straight to storage, and the backend only attaches the photo record once the upload confirms.
A JWT-authenticated API with rate-limited login and an export that reproduces the marketplace's required spreadsheet format.
An admin panel for master data, shift dashboards, exports, and user management.
A separate job card and GST billing system: intake, status workflow, per-line CGST, SGST, and IGST at the correct codes, an invoice lifecycle with a full audit trail, and UPI QR codes on unpaid invoices.
GST reporting built from first principles: auto-numbered and manual invoice series, GSTIN checksum validation, GSTR-1 exports, and a quarterly TDS register.
Five languages in the technician app (English, Hindi, Kannada, Tamil, Malayalam) for multi-region teams.
Notable engineering
Offline-first on flaky warehouse wifi. Local-write-first storage means a power loss or a force-close mid-entry loses nothing, and the sync queue retries with backoff from one minute out to six hours.
Photo upload decoupled from item sync. Each photo has its own retry queue, so a failed photo never blocks the record it belongs to.
GST compliance without an accounting package. Item-wise tax splits, correct HSN and SAC codes, an append-only invoice log, and the GSTR-1 exports were all built in-house and checked against the real filing formats.
A self-hosted stack that runs the whole system, database, storage, both apps, and backups, on a single small VPS for a fraction of the cost of an equivalent managed setup.
Stack
Capabilities demonstrated
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