Thanos Query API returning differnet values for different start and end timestamps

[Kishore Kumar]

Hello Prometheus community,

               I hope the person reading this has a great day.

I am seeing a discrepancy in data that has been returned by API, depending on the start and end time selected.

For a particular timestamp, say 1731304830, the value was different when queried using the following, smaller difference between start and end timestamps. 

1) Query with 6 second difference between start and end timestamp: Value for 1731304830 was 800

<endpoint>/thanosquery/api/v1/query_range?query=sum(increase(envoy_cluster_upstream_rq

{

kubernetes_namespace="sample_namespacce",

kubernetes_pod_name="sample_pod_name",

envoy_cluster_name="sample_cluster_name",

}[3m])/3) 

by (kubernetes_namespace,envoy_cluster_name)

&start=1731304828&end=1731304833&step=1s

2) Query with 60 seconds difference between start and end timestamp: Value for 1731304830 was 40

<endpoint>/thanosquery/api/v1/query_range?query=sum(increase(envoy_cluster_upstream_rq

{

kubernetes_namespace="sample_namespacce",

kubernetes_pod_name="sample_pod_name",

envoy_cluster_name="sample_cluster_name",

}[3m])/3) 

by (kubernetes_namespace,envoy_cluster_name)

&start=1731304800&end=1731304860&step=1s

There were no difference in the query, other than the change in start and end timestamps.

I request to help in understanding why this discrepancy is occurring.

Thank you for your time,

Kishore