k8s: How the controller-runtime Cache Actually Works, and Why Your Controller Does Not Crash the API Server

The article explains that controller-runtime controllers read from a local informer cache, not directly from the API server, and that writes go to the API server while the cache catches up asynchronously via watch events. It also details how shared informers, DeltaFIFO, indexing, cache scoping, APIReader, and cache disabling affect consistency, memory use, and query behavior.

• Source: Kubernetes Official Blog