Offline first, with NFC cards as the network

Most blocks on a palm oil estate have no internet. Field supervisors start their day there, take attendance there, and record every job there. Before GEMA Plantation, they wrote it in a notebook and a clerk typed it into the system later. The office saw yesterday's work at best.

Any app that needs a connection to save a record would simply not get used in that setting. So the first design decision was not about screens. It was about where the data lives.

The phone is the source of truth until upload

Everything a supervisor records is written to a local Room database first: attendance, harvest and upkeep work records (BKM), harvest collection and delivery notes (SPB), with photos and GPS. Nothing waits for the network.

• Records go into an upload queue and are sent whenever the phone finds a signal.
• Every work record has a unique number built from the job and the block, with separate series for harvest (PN) and upkeep (RW). That number is what makes retries safe: sending the same record twice doesn't create a duplicate.
• Once a record reaches the server it is locked, so the copy on the phone and the copy in the office can't drift apart.

When there's no network at all, the card is the network

Saving offline solves one supervisor's problem. But harvest data has to move between people in the field too: the harvest supervisor collects the fruit, and transport needs to know what is being loaded, often in places where neither phone has signal.

For that, GEMA uses NFC cards (Mifare Classic 1K, NDEF). Harvest and load data, and the delivery note, are written to a card on one phone and read on another. When a paper copy is needed, the delivery note can also be printed on a Bluetooth thermal printer.

• No pairing, no hotspot, no internet: tap, write, hand over, tap, read.
• The data still ends up in the same upload queue, so the office sees it as soon as any phone reaches signal.

What it costs

Offline-first is more work than calling an API. Database migrations have to be handled carefully, because a phone in the field may skip several app versions. The upload queue needs retry logic that never duplicates and never silently drops a record. And a 1K card holds very little, so what goes on it has to be chosen carefully.

It is worth it. Supervisors record each job once, in the field, with a photo, a location and a number, and the chain from block to hauling to delivery note stays connected even on days when the estate has no signal at all.