If you zoom into to the 5 minute resolution so you see sub-minute resolution are your graphs smooth?
If you zoom into a fine-grained resolution, the graphs are not expected to be smooth because the metrics are queried using a derivative aggregation, where each data point represents a bucket of time. If there are no documents within that time bucket, then the line chart will go to 0 for that time bucket. Reference: Derivative aggregation | Elasticsearch Guide [8.11] | Elastic
See also: Marvel 2.0 Uneven measurement times result in odd graphs
I set up a test where I index 1 document roughly every 15 seconds. On the Indices overview, when my time range is 30 minutes, my charts look like what I would expect:
When I make the time range 15 minutes, the graphs show zeroes because some of the time buckets shown have 0 doc count - there was no data available to calculate the derivative:
The data sometimes go to zero in my data, but only for non-consecutive data points.