chore: Added some more research

caching.md

@@ -79,10 +79,14 @@
 
 Open source / free version
 
+License evaluation needed
+
 #### Artifactory
 
 Open source / free version
 
+License evaluation needed
+
 #### Artipie
 
 - might be abandoned / low dev activity / needs new maintainer
@@ -94,6 +98,21 @@ Open source / free version
 
 #### kube-image-keeper
 
+[GH](https://github.com/enix/kube-image-keeper)
+
+- Creates a DaemonSet, installing a service on each worker node
+- Works within the cluster and rewrites image coordinates on the fly
+
+- Pro: fine grained caching control
+  - select/exempt images / namespaces
+  - cache invalidation
+- Pro: config within k8s or as k8s objects
+
+- Con: Invasive
+- Con: Rewrites image coordinates using a mutating webhook
+- Con: Must be hosted within each (workload) cluster
+- Con BLOCKER: Cannot handle image digest due to manifest rewrites
+
 #### 'Simple' Squid proxy (or similar)
 
 #### Harbor