I was not able to upload files to my wiki installation:
Unable to create the folder "mwstore://local-backend/local-public/f/fc"
I found out that the wfWikiID() method was generating a non-alphanumeric id. The isValidContainerName method defined in FileBackendStore did not validate the resulting non-alphanumeric container name which prevented every file from being uploaded.
The global wfWikiID() method creates ids by simply combining the database name and prefix.
My database name contains a dot ".".