title: I am having difficulty understanding what is bucket span in MONGODB
body: <p>MongoDB doesn't guarantee that expired data will be deleted immediately upon expiration. Once all documents in a bucket are expired, the background task that removes expired buckets removes the bucket during the next run. The maximum span of time that a single bucket is allowed to cover is controlled by the granularity of the time series collection</p>
  <p>This above paragraph was in the timeseries document of MONGODB,
  &quot;The maximum span of time that a single bucket is allowed to cover&quot;</p>
  <p>What do they mean by this?
  I understand granularity and the specific time span depending on different granularities but I do not understand what does this time span refers to.</p>