public Optional<Long> getCreationTime() {
    return Objects.nonNull(creationTime) ? Optional.of(creationTime) : Optional.empty();
  }
SubscriptionMeta is created for show subscription and is not stored in meta keeper.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/subscription/meta/subscription/SubscriptionMeta.java