// exist.
		gi = newGroupInfo(members)
	} else {
		gi.Members = set.CreateStringSet(append(gi.Members, members...)...).ToSlice()
		gi.UpdatedAt = UTCNow()
	}

	if err := store.saveGroupInfo(ctx, group, gi); err != nil {
		return updatedAt, err
	}

	cache.iamGroupsMap[group] = gi

	// update user-group membership map
	for _, member := range members {
		gset := cache.iamUserGroupMemberships[member]