Query 'min step' of 1m loses fine detail

[bboreham]

I find this setting problemmatic:

cortex-jsonnet/cortex-mixin/dashboards/dashboard-utils.libsonnet

Line 87 in b32d042

interval: '1m',

It is shown in the Grafana UI as 'min step'.

Here it is documented that $__rate_interval will be floored at 4x this quantity, i.e. 4 minutes. This makes it impossible to see fast transients in the data.

Further, Cortex query-frontend will quantise start and end times to a multiple of the step time, so dashboards only change every minute.

Since we are scraping at 15s I propose "min step" should be 15s.