# Mobile clients buffer events offline and upload them hours later

Canonical URL: <https://datadriven.io/problems/mobile-clients-buffer-events-offline-and-upload-them-hours-l-6dd1a757>

Domain: Pipeline Design · Difficulty: medium

## Problem

Mobile clients buffer events offline and upload them hours later. Your 1-minute tumbling window already closed and emitted, so those late events are silently dropped from the counts. Design the stream to account for late arrivals.

## Related

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