I really really like Steampipe to do this kind of query: https://steampipe.io, which is essentially PostgreSQL (literally) to query many different kind of APIs, which means you have access to all PostgreSQL's SQL language can offer to request data.
They have a Kubernetes plugin at https://hub.steampipe.io/plugins/turbot/kubernetes and there are a couple of things I really like:
* it's super easy to request multiple Kubernetes clusters transparently: define one Steampipe "connection" for each of your clusters + define an "aggregator" connection that aggregates all of them, then query the "aggregator" connection. You will get a "context" column that indicates which Kubernetes cluster the row came from. * it's relatively fast in my experience, even for large result sets. It's also possible to configure a caching mechanism inside Steampipe to speed up your queries * it also understands custom resource definitions, although you need to help Steampipe a bit (explained here: https://hub.steampipe.io/plugins/turbot/kubernetes/tables/ku...)
Last but not least: you can of course join multiple "plugins" together. I used it a couple of times to join content exposed only in GCP with content from Kubernetes, that was quite useful.
The things I don't like so much but can be lived with:
* Several columns are just exposed a plain JSON fields ; you need to get familiar with PostgreSQL JSON operators to get something useful. There's a page in Steampipe's doc to explain how to use them better. * Be familiar also with PostgreSQL's common table expressions: there are not so difficult to use but makes the SQL code much easier to read * It's SQL, so you have to know which columns you want to pick before selecting the table they come from ; not ideal from autocompletion * the Steampipe "psql" client is good, but sometimes a bit counter intuitive ; I don't have specific examples but I have the feeling it behaves slightly differently than other CLI client I used.
All in all: I think Steampipe is a cool tool to know about, for Kubernetes but also other API systems.