> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/help-center/help-topics/no-data/webhooks-background-delivery-stopping/background-sync-gaps-and-payload-chunking.md).

# How are background sync gaps and payload size handled?

Background sync gaps are usually **end-user-side**: the wearable hasn't synced to its app, battery-saving mode is on, or (for mobile SDKs) background refresh is disabled or background delivery isn't implemented. The per-provider [debugging FAQ](https://docs.tryterra.co/health-and-fitness-api/debugging-faq) covers each case.

For payload size:

* Responses are automatically chunked only when the requested range exceeds about 28 days.
* For smaller ranges that are still too large, request shorter windows (e.g. 5-day intervals), or ask for payloads to be delivered as a download URL instead of inline data.