Offline Queue

An offline queue is a place on the device itself that stores events when there is no internet, so they can be resent after reconnection and not be lost.

An offline queue is a serious step beyond a memory buffer: a buffer is wiped when the program closes, but an offline queue sits on the device's persistent storage so that even if the user closes the app and reopens it hours later, the events survive and are sent. This is vital for mobile and unstable networks. But that persistence creates two issues an analyst should know: offline-queue events arrive late and often out of order, so their event time diverges from insert time and, on an insert-time chart, produces false spikes; and if the same event was half-sent before the cut, there is a duplication risk that calls for deduplication. The misconception is that an offline queue means no data is ever lost; if the user deletes the app or the queue fills, some is still lost.