private boolean isIndexSegmentUnderCopy(Offset indexSegmentStartOffset) {
    return recoveryStartToken != null && recoveryStartToken.getOffset().equals(indexSegmentStartOffset);
  }
Return true if the index segment is under copy to target persistent index before crashing. This is only used
to check if there were a crash happened before compaction can finish.
@param indexSegmentStartOffset The start {@link Offset} of the {@link IndexSegment}.
@return {@code True} if the index segment is under copy to the target persistent index.
ambry-store/src/main/java/com/github/ambry/store/BlobStoreCompactor.java