private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.memorystore.v1.ZoneDistributionConfig,
            com.google.cloud.memorystore.v1.ZoneDistributionConfig.Builder,
            com.google.cloud.memorystore.v1.ZoneDistributionConfigOrBuilder>
        getZoneDistributionConfigFieldBuilder() {
      if (zoneDistributionConfigBuilder_ == null) {
        zoneDistributionConfigBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.memorystore.v1.ZoneDistributionConfig,
                com.google.cloud.memorystore.v1.ZoneDistributionConfig.Builder,
                com.google.cloud.memorystore.v1.ZoneDistributionConfigOrBuilder>(
                getZoneDistributionConfig(), getParentForChildren(), isClean());
        zoneDistributionConfig_ = null;
      }
      return zoneDistributionConfigBuilder_;
    }
<pre>
Optional. Immutable. Zone distribution configuration of the instance for
node allocation.
</pre>

<code>
.google.cloud.memorystore.v1.ZoneDistributionConfig zone_distribution_config = 18 [(.google.api.field_behavior) = OPTIONAL, (.google.api.field_behavior) = IMMUTABLE];
</code>
java-valkey/proto-google-cloud-valkey-v1/src/main/java/com/google/cloud/memorystore/v1/Instance.java