Enable debug logs (Tools > More tools > Developer options), restart KOReader, start a single metadata search, and look at the relevant bit of log in crash.log (there's two lines detailing the timestamp comparisons).
e.g.,
Code:
05/05/21-18:28:56 DEBUG CalibreSearch:getMetadata: Cache timestamp : 1618434396 2021-04-14T21:06:36.000000+00:00 (2021-04-14 23:06:36 +0200)
05/05/21-18:28:56 DEBUG CalibreSearch:getMetadata: Metadata timestamp: 1618434304 2021-04-14T21:05:04.490813+00:00 (2021-04-14 23:05:04 +0200)
05/05/21-18:28:56 INFO metadata: 565 books imported from cache in 19.190 milliseconds
If you're *only* seeing the performance metric, you're not running a recent enough *nightly* (i.e., Dev channel).
And, extra question, just in case: in which timezone are you?