> 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/faq/help-topics/no-data/historical-backfill-returns-nothing/async-historical-rate-limits.md).

# Why do historical requests only partially arrive?

[Historical data requests](https://docs.tryterra.co/health-and-fitness-api/managing-user-health-data/requesting-historical-data) are processed asynchronously, so the API can return success while the upstream fetch later fails due to provider rate limits. Fitbit and Withings are especially strict.

To handle this:

* Add `retry_if_rate_limited=true` to the request.
* Keep historical windows to roughly a couple of weeks for those providers.
* Rely on automatic webhooks for ongoing data rather than large on-demand pulls.