code: private void handleGroupMembersChanged(final ArtifactStore store,
                                             final Map<ArtifactStore, ArtifactStore> changeMap)
      {
          final StoreKey key = store.getKey();
          if ( StoreType.group == key.getType() )
          {
              final List<StoreKey> newMembers = ( (Group) store ).getConstituents();
              logger.trace( "New members of: {} are: {}", store.getKey(), newMembers );
  
              final Group group = (Group) changeMap.get( store );
              final List<StoreKey> oldMembers = group.getConstituents();
              logger.trace( "Old members of: {} are: {}", group.getName(), oldMembers );
  
              boolean membersChanged = false;
  
              if ( newMembers.size() != oldMembers.size() )
              {
                  membersChanged = true;
              }
              else
              {
                  for ( StoreKey storeKey : newMembers )
                  {
                      if ( !oldMembers.contains( storeKey ) )
                      {
                          membersChanged = true;
                      }
                  }
              }
  
              if ( membersChanged )
              {
                  logger.trace( "Membership change confirmed. Clearing caches for group: {} and groups affected by it.", group.getKey() );
                  clearGroupMetaCache( group, group );
                  try
                  {
                      storeManager.query().getGroupsAffectedBy( group.getKey() ).forEach( g -> clearGroupMetaCache( g, group ) );
                  }
                  catch ( IndyDataException e )
                  {
                      logger.error( String.format( "Can not get affected groups of %s", group.getKey() ), e );
                  }
              }
              else
              {
                  logger.trace( "No members changed, no need to expunge merged metadata" );
              }
          }
      }
docs: If group members changed, should clear the cascading groups metadata cache