diff --git a/core/src/main/java/com/google/cloud/sql/ConnectorConfig.java b/core/src/main/java/com/google/cloud/sql/ConnectorConfig.java
index 1f5e3e456..30c5e8fe5 100644
--- a/core/src/main/java/com/google/cloud/sql/ConnectorConfig.java
+++ b/core/src/main/java/com/google/cloud/sql/ConnectorConfig.java
@@ -19,6 +19,7 @@
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.common.base.Objects;
 import java.util.List;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 /**
@@ -33,6 +34,7 @@ public class ConnectorConfig {
   private final String adminRootUrl;
   private final String adminServicePath;
   private final Supplier<GoogleCredentials> googleCredentialsSupplier;
+  private final Function<String,String> instanceNameResolver;
   private final GoogleCredentials googleCredentials;
   private final String googleCredentialsPath;
   private final String adminQuotaProject;
@@ -50,7 +52,8 @@ private ConnectorConfig(
       String googleCredentialsPath,
       String adminQuotaProject,
       String universeDomain,
-      RefreshStrategy refreshStrategy) {
+      RefreshStrategy refreshStrategy,
+      Function<String,String> instanceNameResolver) {
     this.targetPrincipal = targetPrincipal;
     this.delegates = delegates;
     this.adminRootUrl = adminRootUrl;
@@ -61,6 +64,7 @@ private ConnectorConfig(
     this.adminQuotaProject = adminQuotaProject;
     this.universeDomain = universeDomain;
     this.refreshStrategy = refreshStrategy;
+    this.instanceNameResolver = instanceNameResolver;
   }
 
   @Override
@@ -81,7 +85,8 @@ public boolean equals(Object o) {
         && Objects.equal(googleCredentialsPath, that.googleCredentialsPath)
         && Objects.equal(adminQuotaProject, that.adminQuotaProject)
         && Objects.equal(universeDomain, that.universeDomain)
-        && Objects.equal(refreshStrategy, that.refreshStrategy);
+        && Objects.equal(refreshStrategy, that.refreshStrategy)
+        && Objects.equal(instanceNameResolver, that.instanceNameResolver);
   }
 
   @Override
@@ -96,7 +101,8 @@ public int hashCode() {
         googleCredentialsPath,
         adminQuotaProject,
         universeDomain,
-        refreshStrategy);
+        refreshStrategy,
+        instanceNameResolver);
   }
 
   public String getTargetPrincipal() {
@@ -139,6 +145,10 @@ public RefreshStrategy getRefreshStrategy() {
     return refreshStrategy;
   }
 
+  public Function<String, String> getInstanceNameResolver() {
+    return instanceNameResolver;
+  }
+
   /** The builder for the ConnectionConfig. */
   public static class Builder {
 
@@ -152,6 +162,7 @@ public static class Builder {
     private String adminQuotaProject;
     private String universeDomain;
     private RefreshStrategy refreshStrategy = RefreshStrategy.BACKGROUND;
+    private Function<String,String> instanceNameResolver;
 
     public Builder withTargetPrincipal(String targetPrincipal) {
       this.targetPrincipal = targetPrincipal;
@@ -203,6 +214,10 @@ public Builder withRefreshStrategy(RefreshStrategy refreshStrategy) {
       this.refreshStrategy = refreshStrategy;
       return this;
     }
+    public Builder withInstanceNameResolver(Function<String,String> instanceNameResolver) {
+      this.instanceNameResolver = instanceNameResolver;
+      return this;
+    }
 
     /** Builds a new instance of {@code ConnectionConfig}. */
     public ConnectorConfig build() {
@@ -238,7 +253,8 @@ public ConnectorConfig build() {
           googleCredentialsPath,
           adminQuotaProject,
           universeDomain,
-          refreshStrategy);
+          refreshStrategy,
+          instanceNameResolver);
     }
   }
 }
diff --git a/core/src/main/java/com/google/cloud/sql/InstanceNameResolver.java b/core/src/main/java/com/google/cloud/sql/InstanceNameResolver.java
new file mode 100644
index 000000000..2b009a8f6
--- /dev/null
+++ b/core/src/main/java/com/google/cloud/sql/InstanceNameResolver.java
@@ -0,0 +1,5 @@
+package com.google.cloud.sql;
+
+public interface InstanceNameResolver {
+  String resolve(String name);
+}
diff --git a/core/src/main/java/com/google/cloud/sql/core/ConnectionConfig.java b/core/src/main/java/com/google/cloud/sql/core/ConnectionConfig.java
index 592612c5b..1d913753d 100644
--- a/core/src/main/java/com/google/cloud/sql/core/ConnectionConfig.java
+++ b/core/src/main/java/com/google/cloud/sql/core/ConnectionConfig.java
@@ -63,9 +63,19 @@ public class ConnectionConfig {
 
   private final AuthType authType;
   private final String unixSocketPathSuffix;
+  private final String domainName;
 
   /** Create a new ConnectionConfig from the well known JDBC Connection properties. */
   public static ConnectionConfig fromConnectionProperties(Properties props) {
+    // TODO convert internal uses to fromConnectionProperties(props, domainName)
+    return fromConnectionProperties(props, null);
+  }
+
+  /**
+   * Create a new ConnectionConfig from the well known JDBC Connection properties, also setting
+   * database domain name.
+   */
+  public static ConnectionConfig fromConnectionProperties(Properties props, String domainName) {
     final String csqlInstanceName = props.getProperty(ConnectionConfig.CLOUD_SQL_INSTANCE_PROPERTY);
     final String namedConnection =
         props.getProperty(ConnectionConfig.CLOUD_SQL_NAMED_CONNECTOR_PROPERTY);
@@ -113,6 +123,7 @@ public static ConnectionConfig fromConnectionProperties(Properties props) {
         ipTypes,
         authType,
         unixSocketPathSuffix,
+        domainName,
         new ConnectorConfig.Builder()
             .withTargetPrincipal(targetPrincipal)
             .withDelegates(delegates)
@@ -162,13 +173,20 @@ public boolean equals(Object o) {
         && Objects.equals(unixSocketPath, config.unixSocketPath)
         && Objects.equals(ipTypes, config.ipTypes)
         && Objects.equals(authType, config.authType)
+        && Objects.equals(domainName, config.domainName)
         && Objects.equals(connectorConfig, config.connectorConfig);
   }
 
   @Override
   public int hashCode() {
     return Objects.hash(
-        cloudSqlInstance, namedConnector, unixSocketPath, ipTypes, authType, connectorConfig);
+        cloudSqlInstance,
+        namedConnector,
+        unixSocketPath,
+        ipTypes,
+        authType,
+        domainName,
+        connectorConfig);
   }
 
   private ConnectionConfig(
@@ -178,6 +196,7 @@ private ConnectionConfig(
       List<IpType> ipTypes,
       AuthType authType,
       String unixSocketPathSuffix,
+      String domainName,
       ConnectorConfig connectorConfig) {
     this.cloudSqlInstance = cloudSqlInstance;
     this.namedConnector = namedConnector;
@@ -186,6 +205,7 @@ private ConnectionConfig(
     this.unixSocketPathSuffix = unixSocketPathSuffix;
     this.connectorConfig = connectorConfig;
     this.authType = authType;
+    this.domainName = domainName;
   }
 
   /** Creates a new instance of the ConnectionConfig with an updated connectorConfig. */
@@ -197,9 +217,36 @@ public ConnectionConfig withConnectorConfig(ConnectorConfig config) {
         ipTypes,
         authType,
         unixSocketPathSuffix,
+        domainName,
         config);
   }
 
+  /** Creates a new instance of the ConnectionConfig with an updated cloudSqlInstance. */
+  public ConnectionConfig withCloudSqlInstance(String newCloudSqlInstance) {
+    return new ConnectionConfig(
+        newCloudSqlInstance,
+        namedConnector,
+        unixSocketPath,
+        ipTypes,
+        authType,
+        unixSocketPathSuffix,
+        domainName,
+        connectorConfig);
+  }
+
+  /** Creates a new instance of the ConnectionConfig with an updated cloudSqlInstance. */
+  public ConnectionConfig withDomainName(String domainName) {
+    return new ConnectionConfig(
+        cloudSqlInstance,
+        namedConnector,
+        unixSocketPath,
+        ipTypes,
+        authType,
+        unixSocketPathSuffix,
+        domainName,
+        connectorConfig);
+  }
+
   public String getNamedConnector() {
     return namedConnector;
   }
@@ -228,6 +275,10 @@ public AuthType getAuthType() {
     return authType;
   }
 
+  public String getDomainName() {
+    return domainName;
+  }
+
   /** The builder for the ConnectionConfig. */
   public static class Builder {
 
@@ -238,6 +289,7 @@ public static class Builder {
     private String unixSocketPathSuffix;
     private ConnectorConfig connectorConfig = new ConnectorConfig.Builder().build();
     private AuthType authType = DEFAULT_AUTH_TYPE;
+    private String domainName;
 
     public Builder withCloudSqlInstance(String cloudSqlInstance) {
       this.cloudSqlInstance = cloudSqlInstance;
@@ -275,6 +327,11 @@ public Builder withIpTypes(List<IpType> ipTypes) {
       this.ipTypes = ipTypes;
       return this;
     }
+    /** Set domainName as. */
+    public Builder withDomainName(String domainName) {
+      this.domainName = domainName;
+      return this;
+    }
 
     public Builder withUnixSocketPathSuffix(String unixSocketPathSuffix) {
       this.unixSocketPathSuffix = unixSocketPathSuffix;
@@ -290,6 +347,7 @@ public ConnectionConfig build() {
           ipTypes,
           authType,
           unixSocketPathSuffix,
+          domainName,
           connectorConfig);
     }
   }
diff --git a/core/src/main/java/com/google/cloud/sql/core/Connector.java b/core/src/main/java/com/google/cloud/sql/core/Connector.java
index 14379fcee..b872e8a82 100644
--- a/core/src/main/java/com/google/cloud/sql/core/Connector.java
+++ b/core/src/main/java/com/google/cloud/sql/core/Connector.java
@@ -19,6 +19,7 @@
 import com.google.cloud.sql.ConnectorConfig;
 import com.google.cloud.sql.CredentialFactory;
 import com.google.cloud.sql.RefreshStrategy;
+import com.google.common.base.Strings;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.ListeningScheduledExecutorService;
 import java.io.File;
@@ -28,6 +29,7 @@
 import java.security.KeyPair;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
+import java.util.function.Function;
 import javax.net.ssl.SSLSocket;
 import jnr.unixsocket.UnixSocketAddress;
 import jnr.unixsocket.UnixSocketChannel;
diff --git a/core/src/test/java/com/google/cloud/sql/core/ConnectionConfigTest.java b/core/src/test/java/com/google/cloud/sql/core/ConnectionConfigTest.java
index 0da8b0f62..26f5c5e92 100644
--- a/core/src/test/java/com/google/cloud/sql/core/ConnectionConfigTest.java
+++ b/core/src/test/java/com/google/cloud/sql/core/ConnectionConfigTest.java
@@ -49,6 +49,7 @@ public void testConfigFromProps() {
     final String wantAdminQuotaProject = "myNewProject";
     final String propRefreshStrategy = "Lazy";
     final RefreshStrategy wantRefreshStrategy = RefreshStrategy.LAZY;
+    final String wantDomainName = "db.example.com";
 
     Properties props = new Properties();
     props.setProperty(ConnectionConfig.CLOUD_SQL_INSTANCE_PROPERTY, wantCsqlInstance);
@@ -66,7 +67,7 @@ public void testConfigFromProps() {
         ConnectionConfig.CLOUD_SQL_ADMIN_QUOTA_PROJECT_PROPERTY, wantAdminQuotaProject);
     props.setProperty(ConnectionConfig.CLOUD_SQL_REFRESH_STRATEGY_PROPERTY, propRefreshStrategy);
 
-    ConnectionConfig c = ConnectionConfig.fromConnectionProperties(props);
+    ConnectionConfig c = ConnectionConfig.fromConnectionProperties(props, wantDomainName);
 
     assertThat(c.getCloudSqlInstance()).isEqualTo(wantCsqlInstance);
     assertThat(c.getNamedConnector()).isEqualTo(wantNamedConnector);
@@ -81,6 +82,7 @@ public void testConfigFromProps() {
     assertThat(c.getConnectorConfig().getAdminQuotaProject()).isEqualTo(wantAdminQuotaProject);
     assertThat(c.getUnixSocketPathSuffix()).isEqualTo(wantUnixSuffix);
     assertThat(c.getConnectorConfig().getRefreshStrategy()).isEqualTo(wantRefreshStrategy);
+    assertThat(c.getDomainName()).isEqualTo(wantDomainName);
   }
 
   @Test
@@ -96,6 +98,7 @@ public void testConfigFromBuilder() {
     final String wantAdminServicePath = "sqladmin/";
     final String wantUnixSuffix = ".psql.5432";
     final String wantAdminQuotaProject = "myNewProject";
+    final String wantDomainName = "db.example.com";
 
     ConnectorConfig cc =
         new ConnectorConfig.Builder()
@@ -115,6 +118,7 @@ public void testConfigFromBuilder() {
             .withUnixSocketPath(wantUnixSocket)
             .withUnixSocketPathSuffix(wantUnixSuffix)
             .withConnectorConfig(cc)
+            .withDomainName(wantDomainName)
             .build();
 
     assertThat(c.getCloudSqlInstance()).isEqualTo(wantCsqlInstance);
@@ -128,6 +132,7 @@ public void testConfigFromBuilder() {
     assertThat(c.getConnectorConfig().getAdminServicePath()).isEqualTo(wantAdminServicePath);
     assertThat(c.getConnectorConfig().getAdminQuotaProject()).isEqualTo(wantAdminQuotaProject);
     assertThat(c.getUnixSocketPathSuffix()).isEqualTo(wantUnixSuffix);
+    assertThat(c.getDomainName()).isEqualTo(wantDomainName);
   }
 
   @Test