My team is running a couple thousand cores on GKE and have been in production there for a year. These are multi-tenant clusters with several dozen deployments

My team is running a couple thousand cores on GKE and have been in production there for a year. These are multi-tenant clusters with several dozen deployments of my company's application. "production" tenants get automatically configured SLA monitoring via Pingdom which it's a health endpoint every 30 seconds and has something like a 30 second timeout. Average availability for the year across those environments is 99.99%. I'd say that's decent enough to use. Their support is hilariously bad at times, though.