Progressive Web Apps: Transforming Traditional ERP Systems into Offline-Capable Frontends

The Service Worker & IndexedDB Foundation

Instead of firing direct HTTP requests on every user action, all operational records — barcode scans, order line updates, inspection sign-offs — write synchronously to an IndexedDB object store.

A registered Service Worker intercepts network requests and handles the cache-first routing for static app bundles, guaranteeing sub-100ms UI response times regardless of 3G/4G connectivity states.

“A web application in 2026 should never show a network error screen for standard operations. Persist locally, confirm instantly, sync in the background.”

Handling Conflict Resolution with Vector Clocks

When two warehouse managers update the same pallet quantity while offline, standard Last-Write-Wins (LWW) rules can silently overwrite valid data.

We attach lightweight vector clocks and idempotency hashes to every queued mutation. When the client reconnects, the server processes commutative changes automatically and flags actual logical conflicts for human review with an interactive diff modal.

self.addEventListener("sync", (event: SyncEvent) => {
  if (event.tag === "sync-erp-mutations") {
    event.waitUntil(drainMutationQueue());
  }
});

async function drainMutationQueue() {
  const db = await openDB("erp-offline-store", 1);
  const pending = await db.getAll("mutations");

  for (const item of pending) {
    try {
      await fetch(item.endpoint, {
        method: "POST",
        headers: { "Content-Type": "application/json", "X-Idempotency-Key": item.id },
        body: JSON.stringify(item.payload),
      });
      await db.delete("mutations", item.id);
    } catch (err) {
      console.warn("Retrying sync on next connection window", err);
      break;
    }
  }
}