> Lambda (which is likely built atop the managed kubernetes)

https://news.ycombinator.com/item?id=34964197 (Firecracker internals: Inside the technology powering AWS Lambda (2021)) may interest you, but the short version is no, not on top of kubernetes

Cloud Functions from GCP run on top of knative, one can see it in the metadata: keys, but unknown if it's "vanilla" knative or they have their own knative provider that does further trickery under the hood