After a restore from backup the component database can contain references to files that no longer exist in blob storage. The reconcile component database from blob store task can be used to fix these, but it can take a very long time to run against a large blob store. Typically the files that need to be fixed up with high priority are the repository metadata files. And very typically these are maven files.
On several occasions now we've found that the fastest way to get someone back up and running is to allow the 'repair - rebuild maven metadata' task to recreate hosted metadata files when it encounters one that is an invalid blob reference. A patch to do this has been handed out several times now.
I suggest we productize this change, I don't see much downside to trying to rebuild a maven-metadata.xml file if its corresponding blob file is missing.
If maven-metadata.xml files are not found in the blobstore but the database has a reference to it, rebuild them.