private void checkHeartbeats() {
        long timeout = context.getConfig().getWitnessHeartbeatTimeout();

        for (WitnessRegistration registration : registrations.values()) {
            if (registration.isExpired(timeout)) {
                log.warn("Witness registration expired: {}", registration.getRegistrationId());

                registration.setState(WitnessRegistrationState.EXPIRED);

	return ies.addUser(ctx, user, userType, u, m)
}

func (ies *IAMEtcdStore) addUser(ctx context.Context, user string, userType IAMUserType, u UserIdentity, m map[string]UserIdentity) error {
	if u.Credentials.IsExpired() {
		// Delete expired identity.
		deleteKeyEtcd(ctx, ies.client, getUserIdentityPath(user, userType))
		deleteKeyEtcd(ctx, ies.client, getMappedPolicyPath(user, userType, false))
		return nil
	}

		// validate token for temporary credentials only.
		return nil, ErrInvalidToken
	}

	// Expired credentials must return error right away.
	if cred.IsTemp() && cred.IsExpired() {
		return nil, toAPIErrorCode(r.Context(), errInvalidAccessKeyID)
	}
	secret := globalActiveCred.SecretKey
	if globalSiteReplicationSys.isEnabled() && cred.AccessKey != siteReplicatorSvcAcc {

	err := iamOS.loadIAMConfig(ctx, &u, getUserIdentityPath(user, userType))
	if err != nil {
		if err == errConfigNotFound {
			return u, errNoSuchUser
		}
		return u, err
	}

	if u.Credentials.IsExpired() {
		// Delete expired identity - ignoring errors here.
		iamOS.deleteIAMConfig(ctx, getUserIdentityPath(user, userType))
		iamOS.deleteIAMConfig(ctx, getMappedPolicyPath(user, userType, false))
		return u, errNoSuchUser