FAILED_PRECONDITION: Request failed due to cold cache data on calls to google.people.v1.PeopleService.SearchContacts

Question

I am using the google.people.v1.PeopleService.SearchContacts API to search Google contacts. I am following the instructions from https://developers.google.com/people/api/rest/v1/people/searchContacts that say to warm up the search cache before using the search API. Every request to warm up the cache fails with the error:

FAILED_PRECONDITION: Request failed due to cold cache data. Please try again in 5 seconds.

Repeated attempts after waiting 5+ seconds continue to fail in the same way. It seems that the cache warmup procedure is dependent on the cache already being warm. The same occurs when using Google's API Explorer:

This problem began approximately at 2024-08-02T00:30:00Z and has not been resolved in the roughly 14 hours since.

I have reviewed usage graphs and determined that this is not caused by quota limits or other rate limiting.

What is the cause of this API failure?