In #20875 we added latency config parameter to Metricbeat to handle AWS CloudWatch API delay in exposing S3-related metrics. Without the fix Metricbeat could have returned no data when asking for metrics in <now - 2 x period, now> time interval for small period values.

A similar problem can happen in case of Filebeat CloudWatch input. Filebeat asks for events in <now - period, now> time interval so events that happen close to now timestamp might not be available via CloudWatch API yet. During the next cycle Filebeat asks for <now, now + period> events so the missing events are never retrieved.