PromQL "topk" function is not working as expected

I am trying to display the top 10-services which have high memory usage.

For that I have written the following promql:

sort_desc(topk(5, max by (container)(max_over_time(container_memory_usage_bytes{namespace=~"(ns1|ns2|ns3)", container!=""}[$__interval]))) by (container))

I'm using Bar Gauge visualization and in metric Options -> Type = Instant.

This is still returning all the values and not just top 10.

I tried to follow the recommendations that were made in the similar post on this platform for gauge but couldn't resolve it so looking for other suggestions.

Remove the by (container) grouping from the topk aggregator- you're grouping by your container tag which would mean you're getting the top 5 values per container, so you're getting values for all containers.

Your query should become something like this:

sort_desc(
  topk (
    5,
    max by (container) (
      max_over_time(container_memory_usage_bytes{container!="",namespace=~"(ns1|ns2|ns3)"}[$__interval])
    )
  )
)