@Override
  public FindResult findEntriesSince(String partitionPath, FindToken findToken, long maxTotalSizeOfEntries)
      throws CloudStorageException {
    throw new UnsupportedOperationException("findEntriesSince will not be implemented for AzureCloudDestinationSync");
  }
Just keeping this fn around for tests and legacy reasons but imo this is a horrible function.
The fn takes a list as an arg, why not just a single blob ? It is only ever used to fetch metadata of a blob,
not a list. And because of this design, the higher levels have to wrap the blob-id in a singleton-list.
More importantly, the return type is map. The higher levels have to explicitly look for the result in the map
with blob-id. If there is typo in the code in looking up the map, for eg. instead of storeKey.getId(),
if we type storeKey() alone, then we make a mistake of thinking the blob is not found. Just stop using maps!
Such lookup errors are easy to miss in code-reviews. And most legacy tests are broken beyond repair.
ambry-cloud/src/main/java/com/github/ambry/cloud/azure/AzureCloudDestinationSync.java