diff --git a/Spanner/src/Backup.php b/Spanner/src/Backup.php
index 27dbd8261ff..389f87480d9 100644
--- a/Spanner/src/Backup.php
+++ b/Spanner/src/Backup.php
@@ -124,9 +124,9 @@ public function create(
         }
 
         $request = $this->serializer->decodeMessage(new CreateBackupRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->instance->name());
-
-        return $this->databaseAdminClient->createBackup($request, $callOptions)
+        return $this->databaseAdminClient->createBackup($request, $callOptions + [
+            'resource-prefix' => $this->instance->name(),
+        ])
             ->withResultFunction($this->backupResultFunction());
     }
 
@@ -168,9 +168,10 @@ public function createCopy(
         ];
 
         $request = $this->serializer->decodeMessage(new CopyBackupRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->instance->name());
 
-        return $this->databaseAdminClient->copyBackup($request, $callOptions)
+        return $this->databaseAdminClient->copyBackup($request, $callOptions + [
+            'resource-prefix' => $this->instance->name(),
+        ])
             ->withResultFunction($this->backupResultFunction());
     }
 
@@ -193,9 +194,10 @@ public function delete(array $options = []): void
         ];
 
         $request = $this->serializer->decodeMessage(new DeleteBackupRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $this->databaseAdminClient->deleteBackup($request, $callOptions);
+        $this->databaseAdminClient->deleteBackup($request, $callOptions + [
+            'resource-prefix' => $this->name,
+        ]);
     }
 
     /**
@@ -277,9 +279,10 @@ public function reload(array $options = []): array
         ];
 
         $request = $this->serializer->decodeMessage(new GetBackupRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $response = $this->databaseAdminClient->getBackup($request, $callOptions);
+        $response = $this->databaseAdminClient->getBackup($request, $callOptions + [
+            'resource-prefix' => $this->name,
+        ]);
         return $this->info = $this->handleResponse($response);
     }
 
@@ -340,9 +343,10 @@ public function updateExpireTime(DateTimeInterface $newTimestamp, array $options
         ];
 
         $request = $this->serializer->decodeMessage(new UpdateBackupRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $response = $this->databaseAdminClient->updateBackup($request, $callOptions);
+        $response = $this->databaseAdminClient->updateBackup($request, $callOptions + [
+            'resource-prefix' => $this->name,
+        ]);
         return $this->info = $this->handleResponse($response);
     }
 
diff --git a/Spanner/src/Database.php b/Spanner/src/Database.php
index 8e3c89678a1..60f11122465 100644
--- a/Spanner/src/Database.php
+++ b/Spanner/src/Database.php
@@ -358,9 +358,10 @@ public function reload(array $options = []): array
         $data['name'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new GetDatabaseRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $response = $this->databaseAdminClient->getDatabase($request, $callOptions);
+        $response = $this->databaseAdminClient->getDatabase($request, $callOptions + [
+            'resource-prefix' => $this->name,
+        ]);
         return $this->info = $this->handleResponse($response);
     }
 
@@ -423,9 +424,9 @@ public function create(array $options = []): OperationResponse
         ];
 
         $request = $this->serializer->decodeMessage(new CreateDatabaseRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->instance->name());
-
-        return $this->databaseAdminClient->createDatabase($request, $callOptions)
+        return $this->databaseAdminClient->createDatabase($request, $callOptions + [
+            'resource-prefix' => $this->instance->name(),
+        ])
             ->withResultFunction($this->databaseResultFunction());
     }
 
@@ -488,9 +489,10 @@ public function updateDatabase(array $options = []): OperationResponse
         ];
 
         $request = $this->serializer->decodeMessage(new UpdateDatabaseRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        return $this->databaseAdminClient->updateDatabase($request, $callOptions)
+        return $this->databaseAdminClient->updateDatabase($request, $callOptions + [
+            'resource-prefix' => $this->name,
+        ])
             ->withResultFunction($this->databaseResultFunction());
     }
 
@@ -563,9 +565,9 @@ public function updateDdlBatch(array $statements, array $options = []): Operatio
         ];
 
         $request = $this->serializer->decodeMessage(new UpdateDatabaseDdlRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
-
-        return $this->databaseAdminClient->updateDatabaseDdl($request, $callOptions);
+        return $this->databaseAdminClient->updateDatabaseDdl($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ]);
     }
 
     /**
@@ -596,9 +598,10 @@ public function drop(array $options = []): void
         $data['database'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new DropDatabaseRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $this->databaseAdminClient->dropDatabase($request, $callOptions);
+        $this->databaseAdminClient->dropDatabase($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ]);
 
         if ($this->sessionPool) {
             $this->sessionPool->clear();
@@ -633,9 +636,10 @@ public function ddl(array $options = []): array
         $data['database'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new GetDatabaseDdlRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $response = $this->databaseAdminClient->getDatabaseDdl($request, $callOptions);
+        $response = $this->databaseAdminClient->getDatabaseDdl($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ]);
         $ddl = $this->handleResponse($response);
 
         if (isset($ddl['statements'])) {
@@ -1683,7 +1687,6 @@ public function execute($sql, array $options = []): Result
             $options['transaction'],
             $options['transactionContext']
         ) = $this->transactionSelector($options);
-        $options = $this->addLarHeader($options, true, $options['transactionContext']);
 
         $options['directedReadOptions'] = $this->configureDirectedReadOptions(
             $options,
@@ -1693,7 +1696,9 @@ public function execute($sql, array $options = []): Result
         try {
             // Unset the internal flag.
             unset($options['singleUse']);
-            return $this->operation->execute($session, $sql, $options);
+            return $this->operation->execute($session, $sql, $options + [
+                'route-to-leader' => $options['transactionContext'] === SessionPoolInterface::CONTEXT_READWRITE
+            ]);
         } finally {
             $session->setExpiration();
         }
@@ -1782,10 +1787,11 @@ public function batchWrite(array $mutationGroups, array $options = []): \Generat
             ];
 
             $request = $this->serializer->decodeMessage(new BatchWriteRequest(), $data);
-            $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
-            $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
 
-            $response = $this->spannerClient->batchWrite($request, $callOptions);
+            $response = $this->spannerClient->batchWrite($request, $callOptions + [
+                'resource-prefix' => $this->name,
+                'route-to-leader' => $this->routeToLeader,
+            ]);
             return $this->handleResponse($response);
         } finally {
             $this->isRunningTransaction = false;
@@ -1927,11 +1933,10 @@ public function executePartitionedUpdate($statement, array $options = []): int
         }
         $transaction = $this->operation->transaction($session, $beginTransactionOptions);
 
-        $options = $this->addLarHeader($options);
-
         try {
             return $this->operation->executeUpdate($session, $transaction, $statement, [
-                'statsItem' => 'rowCountLowerBound'
+                'statsItem' => 'rowCountLowerBound',
+                'route-to-leader' => true,
             ] + $options);
         } finally {
             $session->setExpiration();
@@ -2072,12 +2077,12 @@ public function read($table, KeySet $keySet, array $columns, array $options = []
             $this->directedReadOptions ?? []
         );
 
-        $options = $this->addLarHeader($options, true, $context);
-
         try {
             // Unset the internal flag.
             unset($options['singleUse']);
-            return $this->operation->read($session, $table, $keySet, $columns, $options);
+            return $this->operation->read($session, $table, $keySet, $columns, $options + [
+                'route-to-leader' => $context === SessionPoolInterface::CONTEXT_READ
+            ]);
         } finally {
             $session->setExpiration();
         }
@@ -2203,10 +2208,10 @@ public function batchCreateSessions(array $options): array
         $data['database'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new BatchCreateSessionsRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
-
-        $response = $this->spannerClient->batchCreateSessions($request, $callOptions);
+        $response = $this->spannerClient->batchCreateSessions($request, $callOptions + [
+            'resource-prefix' => $this->name,
+            'route-to-leader' => $this->routeToLeader
+        ]);
         return $this->handleResponse($response);
     }
 
@@ -2225,9 +2230,9 @@ public function deleteSessionAsync(array $options): PromiseInterface
         [$data, $callOptions] = $this->splitOptionalArgs($options);
 
         $request = $this->serializer->decodeMessage(new DeleteSessionRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
-
-        return $this->spannerClient->deleteSessionAsync($request, $callOptions);
+        return $this->spannerClient->deleteSessionAsync($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ]);
     }
 
     /**
@@ -2254,14 +2259,13 @@ public function deleteSessionAsync(array $options): PromiseInterface
     public function backupOperations(array $options = []): ItemIterator
     {
         [$data, $callOptions] = $this->splitOptionalArgs($options);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
         $request = $this->serializer->decodeMessage(new ListBackupOperationsRequest(), $data);
         $request->setParent($this->instance->name());
 
         return $this->buildLongRunningIterator(
             [$this->databaseAdminClient, 'listBackupOperations'],
             $request,
-            $callOptions
+            $callOptions +  ['resource-prefix' => $this->name]
         );
     }
 
@@ -2286,9 +2290,9 @@ public function createDatabaseFromBackup($name, $backup, array $options = []): O
         ];
 
         $request = $this->serializer->decodeMessage(new RestoreDatabaseRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
-
-        return $this->databaseAdminClient->restoreDatabase($request, $callOptions)
+        return $this->databaseAdminClient->restoreDatabase($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ])
             ->withResultFunction($this->databaseResultFunction());
     }
 
@@ -2316,14 +2320,13 @@ public function createDatabaseFromBackup($name, $backup, array $options = []): O
     public function databaseOperations(array $options = []): ItemIterator
     {
         [$data, $callOptions] = $this->splitOptionalArgs($options);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
         $request = $this->serializer->decodeMessage(new ListDatabaseOperationsRequest(), $data);
         $request->setParent($this->instance->name());
 
         return $this->buildLongRunningIterator(
             [$this->databaseAdminClient, 'listDatabaseOperations'],
             $request,
-            $callOptions
+            $callOptions + ['resource-prefix' => $this->name]
         );
     }
 
diff --git a/Spanner/src/Instance.php b/Spanner/src/Instance.php
index 034b41fee09..e9365607e1d 100644
--- a/Spanner/src/Instance.php
+++ b/Spanner/src/Instance.php
@@ -198,9 +198,10 @@ public function exists(array $options = []): bool
                     'fieldMask' => ['paths' => ['name']],
                 ];
                 $request = $this->serializer->decodeMessage(new GetInstanceRequest(), $data);
-                $callOptions = $this->addResourcePrefixHeader($callOptions, $this->projectName);
 
-                $this->instanceAdminClient->getInstance($request, $callOptions);
+                $this->instanceAdminClient->getInstance($request, $callOptions + [
+                    'resource-prefix' => $this->projectName
+                ]);
             } else {
                 $this->reload($options);
             }
@@ -252,9 +253,10 @@ public function reload(array $options = []): array
         }
 
         $request = $this->serializer->decodeMessage(new GetInstanceRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->projectName);
 
-        $response = $this->instanceAdminClient->getInstance($request, $callOptions);
+        $response = $this->instanceAdminClient->getInstance($request, $callOptions + [
+            'resource-prefix' => $this->projectName
+        ]);
         return $this->info = $this->handleResponse($response);
     }
 
@@ -303,9 +305,10 @@ public function create(InstanceConfiguration $config, array $options = []): Oper
         ];
 
         $request = $this->serializer->decodeMessage(new CreateInstanceRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        return $this->instanceAdminClient->createInstance($request, $callOptions)
+        return $this->instanceAdminClient->createInstance($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ])
             ->withResultFunction($this->instanceResultFunction());
     }
 
@@ -382,9 +385,10 @@ public function update(array $options = []): OperationResponse
         ];
 
         $request = $this->serializer->decodeMessage(new UpdateInstanceRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        return $this->instanceAdminClient->updateInstance($request, $callOptions)
+        return $this->instanceAdminClient->updateInstance($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ])
             ->withResultFunction($this->instanceResultFunction());
     }
 
@@ -409,9 +413,10 @@ public function delete(array $options = []): void
         $data['name'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new DeleteInstanceRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
-        $this->instanceAdminClient->deleteInstance($request, $callOptions);
+        $this->instanceAdminClient->deleteInstance($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ]);
     }
 
     /**
@@ -539,12 +544,11 @@ public function databases(array $options = []): ItemIterator
         $data['parent'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new ListDatabasesRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
         return $this->buildListItemsIterator(
             [$this->databaseAdminClient, 'listDatabases'],
             $request,
-            $callOptions,
+            $callOptions + ['resource-prefix' => $this->name],
             function (array $database) {
                 return $this->database($database['name'], ['database' => $database]);
             },
@@ -614,12 +618,11 @@ public function backups(array $options = []): ItemIterator
         $data['parent'] = $this->name;
 
         $request = $this->serializer->decodeMessage(new ListBackupsRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
         return $this->buildListItemsIterator(
             [$this->databaseAdminClient, 'listBackups'],
             $request,
-            $callOptions,
+            $callOptions + ['resource-prefix' => $this->name],
             function (array $backup) {
                 return $this->backup($backup['name'], $backup);
             },
diff --git a/Spanner/src/InstanceConfiguration.php b/Spanner/src/InstanceConfiguration.php
index 9f5ba1774d7..c58ecc61da4 100644
--- a/Spanner/src/InstanceConfiguration.php
+++ b/Spanner/src/InstanceConfiguration.php
@@ -170,15 +170,12 @@ public function reload(array $options = [])
     {
         [$data, $callOptions] = $this->splitOptionalArgs($options);
         $data += ['name' => $this->name];
-        $callOptions = $this->addResourcePrefixHeader(
-            $callOptions,
-            InstanceAdminClient::projectName($this->projectId)
-        );
 
-        $response = $this->instanceAdminClient->getInstanceConfig(
-            $this->serializer->decodeMessage(new GetInstanceConfigRequest(), $data),
-            $callOptions
-        );
+        $request = $this->serializer->decodeMessage(new GetInstanceConfigRequest(), $data);
+
+        $response = $this->instanceAdminClient->getInstanceConfig($request, $callOptions + [
+            'resource-prefix' => InstanceAdminClient::projectName($this->projectId),
+        ]);
 
         return $this->info = $this->handleResponse($response);
     }
@@ -241,11 +238,10 @@ public function create(InstanceConfiguration $baseConfig, array $replicas, array
             new CreateInstanceConfigRequest(),
             $requestArray
         );
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
         $operationResponse = $this->instanceAdminClient->createInstanceConfig(
             $request,
-            $callOptions
+            $callOptions + ['resource-prefix' => $this->name]
         );
 
         return $operationResponse
@@ -291,11 +287,10 @@ public function update(array $options = [])
             'updateMask' => $this->fieldMask($data),
             'validateOnly' => $validateOnly
         ]);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->name);
 
         $operationResponse = $this->instanceAdminClient->updateInstanceConfig(
             $request,
-            $callOptions
+            $callOptions + ['resource-prefix' => $this->name]
         );
 
         return $operationResponse
@@ -323,10 +318,11 @@ public function delete(array $options = [])
         [$data, $callOptions] = $this->splitOptionalArgs($options);
         $data += ['name' => $this->name];
 
-        $this->instanceAdminClient->deleteInstanceConfig(
-            $this->serializer->decodeMessage(new DeleteInstanceConfigRequest(), $data),
-            $this->addResourcePrefixHeader($callOptions, $this->name)
-        );
+        $request = $this->serializer->decodeMessage(new DeleteInstanceConfigRequest(), $data);
+
+        $this->instanceAdminClient->deleteInstanceConfig($request, $callOptions + [
+            'resource-prefix' => $this->name
+        ]);
     }
 
     /**
diff --git a/Core/src/Middleware/ExceptionMiddleware.php b/Spanner/src/Middleware/SpannerMiddleware.php
similarity index 74%
rename from Core/src/Middleware/ExceptionMiddleware.php
rename to Spanner/src/Middleware/SpannerMiddleware.php
index 212c76acc2c..1bfca02c829 100644
--- a/Core/src/Middleware/ExceptionMiddleware.php
+++ b/Spanner/src/Middleware/SpannerMiddleware.php
@@ -30,32 +30,42 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-namespace Google\Cloud\Core\Middleware;
+namespace Google\Cloud\Spanner\Middleware;
 
+use Google\ApiCore\ArrayTrait;
 use Google\ApiCore\ApiException;
 use Google\ApiCore\BidiStream;
 use Google\ApiCore\Call;
 use Google\ApiCore\ClientStream;
 use Google\ApiCore\Middleware\MiddlewareInterface;
-use Google\ApiCore\Serializer;
+use Google\Cloud\Spanner\Serializer;
 use Google\ApiCore\ServerStream;
 use Google\Cloud\Core\RequestProcessorTrait;
 use GuzzleHttp\Promise\PromiseInterface;
 use Throwable;
 
 /**
- * Middleware that wraps any Api Exception to a `Google\Cloud\Core\Exception`
- * exception class. This is primarily to maintain backwards compatibility with
- * previous Spanner versions.
+ * Middleware for Spanner that adds the following functionality:
+ *
+ *  - Wraps any Api Exception to a `Google\Cloud\Core\Exception` exception
+ *    class. This is primarily to maintain backwards compatibility with previous
+ *    Spanner versions.
+ *  -
  *
  * @internal
  */
-class ExceptionMiddleware implements MiddlewareInterface
+class SpannerMiddleware implements MiddlewareInterface
 {
+    use ArrayTrait;
+
+    private const ROUTE_TO_LEADER_HEADER = 'x-goog-spanner-route-to-leader';
+    private const RESOURCE_PREFIX_HEADER = 'google-cloud-resource-prefix';
+
     use RequestProcessorTrait;
 
     /** @var callable */
     private $nextHandler;
+    private $serializer;
 
     public function __construct(callable $nextHandler)
     {
@@ -71,6 +81,14 @@ public function __construct(callable $nextHandler)
      */
     public function __invoke(Call $call, array $options)
     {
+        if ($resourcePrefix = $this->pluck('resource-prefix', $options, false)) {
+            $options['headers'][self::RESOURCE_PREFIX_HEADER] = [$options['resource-prefix']];
+        }
+
+        if (true === $this->pluck('route-to-leader', $options, false)) {
+            $options['headers'][self::ROUTE_TO_LEADER_HEADER] = ['true'];
+        }
+
         $response = ($this->nextHandler)($call, $options);
         if ($response instanceof PromiseInterface) {
             return $response->then(null, function ($value) {
@@ -82,6 +100,7 @@ public function __invoke(Call $call, array $options)
                 }
             });
         }
+
         // this can also be a Stream
         return $response;
     }
diff --git a/Spanner/src/Operation.php b/Spanner/src/Operation.php
index 22451bd377c..283f5629b29 100644
--- a/Spanner/src/Operation.php
+++ b/Spanner/src/Operation.php
@@ -17,6 +17,8 @@
 
 namespace Google\Cloud\Spanner;
 
+use Google\Cloud\Core\ApiHelperTrait;
+use Google\Cloud\Core\RequestProcessorTrait;
 use Google\Cloud\Spanner\Batch\QueryPartition;
 use Google\Cloud\Spanner\Batch\ReadPartition;
 use Google\Cloud\Spanner\Session\Session;
@@ -47,7 +49,8 @@
  */
 class Operation
 {
-    use RequestTrait;
+    use ApiHelperTrait;
+    use RequestProcessorTrait;
     use MutationTrait;
 
     const OP_INSERT = 'insert';
@@ -163,10 +166,10 @@ public function commitWithResponse(Session $session, array $mutations, array $op
         $data = $this->formatSingleUseTransactionOptions($data);
 
         $request = $this->serializer->decodeMessage(new CommitRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->getDatabaseNameFromSession($session));
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
-
-        $response = $this->spannerClient->commit($request, $callOptions);
+        $response = $this->spannerClient->commit($request, $callOptions + [
+            'resource-prefix' => $this->getDatabaseNameFromSession($session),
+            'route-to-leader' => $this->routeToLeader
+        ]);
         $timestamp = $response->getCommitTimestamp();
 
         return [
@@ -202,10 +205,10 @@ public function rollback(Session $session, $transactionId, array $options = []):
         ];
 
         $request = $this->serializer->decodeMessage(new RollbackRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->getDatabaseNameFromSession($session));
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
-
-        $this->spannerClient->rollback($request, $callOptions);
+        $this->spannerClient->rollback($request, $callOptions + [
+            'resource-prefix' => $this->getDatabaseNameFromSession($session),
+            'route-to-leader' => $this->routeToLeader
+        ]);
     }
 
     /**
@@ -377,10 +380,10 @@ public function executeUpdateBatch(
         ];
 
         $request = $this->serializer->decodeMessage(new ExecuteBatchDmlRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->getDatabaseNameFromSession($session));
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
-
-        $response = $this->spannerClient->executeBatchDml($request, $callOptions);
+        $response = $this->spannerClient->executeBatchDml($request, $callOptions + [
+            'resource-prefix' => $this->getDatabaseNameFromSession($session),
+            'route-to-leader' => $this->routeToLeader
+        ]);
         $res = $this->handleResponse($response);
 
         if (empty($transaction->id())) {
@@ -663,10 +666,10 @@ public function createSession($databaseName, array $options = []): Session
 
         $request = $this->serializer->decodeMessage(new CreateSessionRequest(), $data);
 
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $databaseName);
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
-
-        $response = $this->spannerClient->createSession($request, $callOptions);
+        $response = $this->spannerClient->createSession($request, $callOptions + [
+            'resource-prefix' => $databaseName,
+            'route-to-leader' => $this->routeToLeader
+        ]);
         $res = $this->handleResponse($response);
 
         return $this->session($res['name']);
@@ -753,10 +756,11 @@ public function partitionQuery(
         ];
 
         $request = $this->serializer->decodeMessage(new PartitionQueryRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->getDatabaseNameFromSession($session));
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
 
-        $response = $this->spannerClient->partitionQuery($request, $callOptions);
+        $response = $this->spannerClient->partitionQuery($request, $callOptions + [
+            'resource-prefix' => $this->getDatabaseNameFromSession($session),
+            'route-to-leader' => $this->routeToLeader
+        ]);
         $res = $this->handleResponse($response);
 
         $partitions = [];
@@ -816,10 +820,11 @@ public function partitionRead(
         ];
 
         $request = $this->serializer->decodeMessage(new PartitionReadRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->getDatabaseNameFromSession($session));
-        $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
 
-        $response = $this->spannerClient->partitionRead($request, $callOptions);
+        $response = $this->spannerClient->partitionRead($request, $callOptions + [
+            'resource-prefix' => $this->getDatabaseNameFromSession($session),
+            'route-to-leader' => $this->routeToLeader
+        ]);
         $res = $this->handleResponse($response);
 
         $partitions = [];
@@ -866,19 +871,21 @@ private function beginTransaction(Session $session, array $options = []): array
         $transactionOptions = $this->formatTransactionOptions(
             $this->pluck('transactionOptions', $data, false) ?: []
         );
-        if (isset($transactionOptions['readWrite'])
-            || isset($transactionOptions['partitionedDml'])) {
-            $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
-        }
+        $routeToLeader = (
+            isset($transactionOptions['readWrite']) || isset($transactionOptions['partitionedDml'])
+        ) && $this->routeToLeader;
+
         $data += [
             'session' => $session->name(),
             'options' => $transactionOptions
         ];
 
         $request = $this->serializer->decodeMessage(new BeginTransactionRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->getDatabaseNameFromSession($session));
 
-        $response = $this->spannerClient->beginTransaction($request, $callOptions);
+        $response = $this->spannerClient->beginTransaction($request, $callOptions + [
+            'resource-prefix' => $this->getDatabaseNameFromSession($session),
+            'route-to-leader' => $routeToLeader,
+        ]);
         return $this->handleResponse($response);
     }
 
@@ -1066,17 +1073,21 @@ private function formatTransactionOptions(array $transactionOptions): array
      */
     private function executeStreamingSql(array $args)
     {
-        list($data, $callOptions) = $this->splitOptionalArgs($args);
+        list($data, $callOptions) = $this->splitOptionalArgs($args, ['route-to-leader']);
         $data = $this->formatSqlParams($data);
         $data['transaction'] = $this->createTransactionSelector($data);
         $data['queryOptions'] = $this->createQueryOptions($data);
-        $callOptions = $this->conditionallyUnsetLarHeader($callOptions, $this->routeToLeader);
+        if (!$this->routeToLeader) {
+            unset($callOptions['route-to-leader']);
+        }
+
         $databaseName = $this->pluck('database', $data);
 
         $request = $this->serializer->decodeMessage(new ExecuteSqlRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $databaseName);
 
-        $response = $this->spannerClient->executeStreamingSql($request, $callOptions);
+        $response = $this->spannerClient->executeStreamingSql($request, $callOptions + [
+            'resource-prefix' => $databaseName,
+        ]);
         return $this->handleResponse($response);
     }
 
@@ -1086,15 +1097,18 @@ private function executeStreamingSql(array $args)
      */
     private function streamingRead(array $args): \Generator
     {
-        list($data, $callOptions) = $this->splitOptionalArgs($args);
+        list($data, $callOptions) = $this->splitOptionalArgs($args, ['route-to-leader']);
         $data['transaction'] = $this->createTransactionSelector($data);
-        $callOptions = $this->conditionallyUnsetLarHeader($callOptions, $this->routeToLeader);
+        if (!$this->routeToLeader) {
+            unset($callOptions['route-to-leader']);
+        }
         $databaseName = $this->pluck('database', $data);
 
         $request = $this->serializer->decodeMessage(new ReadRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $databaseName);
 
-        $response = $this->spannerClient->streamingRead($request, $callOptions);
+        $response = $this->spannerClient->streamingRead($request, $callOptions + [
+            'resource-prefix' => $databaseName,
+        ]);
 
         return $this->handleResponse($response);
     }
@@ -1132,23 +1146,6 @@ private function formatPartitionQueryOptions(array $args): array
         return $args;
     }
 
-    /**
-     * Conditionally unset the LAR header.
-     *
-     * @param array $args Request arguments.
-     * @param bool $value Whether to set or unset the LAR header.
-     * @return array
-     */
-    private function conditionallyUnsetLarHeader(
-        array $args,
-        bool $value = true
-    ): array {
-        if (!$value) {
-            unset($args['headers'][$this->larHeader]);
-        }
-        return $args;
-    }
-
     /**
      * Represent the class in a more readable and digestable fashion.
      *
diff --git a/Spanner/src/RequestTrait.php b/Spanner/src/RequestTrait.php
index e335cf09466..10d9d3e1dcb 100644
--- a/Spanner/src/RequestTrait.php
+++ b/Spanner/src/RequestTrait.php
@@ -36,45 +36,6 @@ trait RequestTrait
     use ApiHelperTrait;
     use RequestProcessorTrait;
 
-    private $larHeader = 'x-goog-spanner-route-to-leader';
-    private $resourcePrefixHeader = 'google-cloud-resource-prefix';
-
-    /**
-     * Add the `x-goog-spanner-route-to-leader` header value to the request.
-     *
-     * @param array $args Request arguments.
-     * @param bool $value LAR header value.
-     * @param string $context Transaction context.
-     * @return array
-     */
-    private function addLarHeader(
-        array $args,
-        bool $value = true,
-        string $context = SessionPoolInterface::CONTEXT_READWRITE
-    ) {
-        if (!$value) {
-            return $args;
-        }
-        // If value is true and context is READWRITE, set LAR header.
-        if ($context === SessionPoolInterface::CONTEXT_READWRITE) {
-            $args['headers'][$this->larHeader] = ['true'];
-        }
-        return $args;
-    }
-
-    /**
-     * Add the `google-cloud-resource-prefix` header value to the request.
-     *
-     * @param array $args Request arguments.
-     * @param string $value Resource prefix header value.
-     * @return array
-     */
-    private function addResourcePrefixHeader(array $args, string $value)
-    {
-        $args['headers'][$this->resourcePrefixHeader] = [$value];
-        return $args;
-    }
-
     /**
      * Helper making list calls for long running operations.
      *
diff --git a/Spanner/src/Session/Session.php b/Spanner/src/Session/Session.php
index f293d8e12c5..a081d4b0c76 100644
--- a/Spanner/src/Session/Session.php
+++ b/Spanner/src/Session/Session.php
@@ -17,9 +17,9 @@
 
 namespace Google\Cloud\Spanner\Session;
 
+use Google\Cloud\Core\ApiHelperTrait;
 use Google\Cloud\Core\Exception\NotFoundException;
 use Google\Cloud\Spanner\Database;
-use Google\Cloud\Spanner\RequestTrait;
 use Google\Cloud\Spanner\Serializer;
 use Google\Cloud\Spanner\V1\Client\SpannerClient;
 use Google\Cloud\Spanner\V1\DeleteSessionRequest;
@@ -30,7 +30,7 @@
  */
 class Session
 {
-    use RequestTrait;
+    use ApiHelperTrait;
 
     /**
      * @var int|null
@@ -117,10 +117,11 @@ public function exists(array $options = [])
 
         try {
             $request = $this->serializer->decodeMessage(new GetSessionRequest(), $data);
-            $callOptions = $this->addResourcePrefixHeader($callOptions, $this->databaseName);
-            $callOptions = $this->addLarHeader($callOptions, $this->routeToLeader);
 
-            $this->spannerClient->getSession($request, $callOptions);
+            $this->spannerClient->getSession($request, $callOptions + [
+                'resource-prefix' => $this->databaseName,
+                'route-to-leader' => $this->routeToLeader,
+            ]);
         } catch (NotFoundException $e) {
             return false;
         }
@@ -141,9 +142,10 @@ public function delete(array $options = [])
         ];
 
         $request = $this->serializer->decodeMessage(new DeleteSessionRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->databaseName);
 
-        $this->spannerClient->deleteSession($request, $callOptions);
+        $this->spannerClient->deleteSession($request, $callOptions + [
+            'resource-prefix' => $this->databaseName,
+        ]);
     }
 
     /**
diff --git a/Spanner/src/SpannerClient.php b/Spanner/src/SpannerClient.php
index 8b3f9655cdb..600d1b82a55 100644
--- a/Spanner/src/SpannerClient.php
+++ b/Spanner/src/SpannerClient.php
@@ -34,6 +34,7 @@
 use Google\Cloud\Spanner\Admin\Instance\V1\ListInstanceConfigsRequest;
 use Google\Cloud\Spanner\Admin\Instance\V1\ListInstancesRequest;
 use Google\Cloud\Spanner\Admin\Instance\V1\ReplicaInfo;
+use Google\Cloud\Spanner\Admin\Instance\V1\InstanceConfig;
 use Google\Cloud\Spanner\Batch\BatchClient;
 use Google\Cloud\Spanner\Middleware\SpannerMiddleware;
 use Google\Cloud\Spanner\Session\SessionPoolInterface;
@@ -255,17 +256,21 @@ public function __construct(array $config = [])
             'libName' => 'gccl',
             'serializer' => $this->serializer,
         ];
-        $middleware = function (MiddlewareInterface $handler) {
-            return new SpannerMiddleware($handler);
-        };
         $this->spannerClient = $config['gapicSpannerClient'] ?? new GapicSpannerClient($clientConfig);
-        $this->spannerClient->addMiddleware($middleware);
         $this->instanceAdminClient = $config['gapicSpannerInstanceAdminClient']
             ?? new InstanceAdminClient($clientConfig);
-        $this->instanceAdminClient->addMiddleware($middleware);
         $this->databaseAdminClient = $config['gapicSpannerDatabaseAdminClient']
             ?? new DatabaseAdminClient($clientConfig);
+
+        // Add the SpannerMiddleware, which wraps API Exceptions, and adds
+        // Resource Prefix and LAR headers
+        $middleware = function (MiddlewareInterface $handler) {
+            return new SpannerMiddleware($handler);
+        };
+        $this->spannerClient->addMiddleware($middleware);
+        $this->instanceAdminClient->addMiddleware($middleware);
         $this->databaseAdminClient->addMiddleware($middleware);
+
         $this->projectName = InstanceAdminClient::projectName($this->projectId);
     }
 
@@ -410,12 +415,11 @@ public function instanceConfigurations(array $options = [])
         $data['parent'] = $this->projectName;
 
         $request = $this->serializer->decodeMessage(new ListInstanceConfigsRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->projectName);
 
         return $this->buildListItemsIterator(
             [$this->instanceAdminClient, 'listInstanceConfigs'],
             $request,
-            $callOptions,
+            $callOptions + ['resource-prefix' => $this->projectName],
             function (array $config) {
                 return $this->instanceConfiguration($config['name'], $config);
             },
@@ -486,14 +490,13 @@ public function instanceConfiguration($name, array $options = [])
     public function instanceConfigOperations(array $options = [])
     {
         [$data, $callOptions] = $this->splitOptionalArgs($options);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->projectName);
         $request = $this->serializer->decodeMessage(new ListInstanceConfigOperationsRequest(), $data);
         $request->setParent($this->projectName);
 
         return $this->buildLongRunningIterator(
             [$this->instanceAdminClient, 'listInstanceConfigOperations'],
             $request,
-            $callOptions,
+            $callOptions + ['resource-prefix' => $this->projectName],
             function (Operation $operation) {
                 return $this->resumeOperation(
                     $operation->getName(),
@@ -598,12 +601,11 @@ public function instances(array $options = [])
         $data += ['filter' => '', 'parent' => $this->projectName];
 
         $request = $this->serializer->decodeMessage(new ListInstancesRequest(), $data);
-        $callOptions = $this->addResourcePrefixHeader($callOptions, $this->projectName);
 
         return $this->buildListItemsIterator(
             [$this->instanceAdminClient, 'listInstances'],
             $request,
-            $callOptions,
+            $callOptions + ['resource-prefix' => $this->projectName],
             function (array $instance) {
                 $name = InstanceAdminClient::parseName($instance['name'])['instance'];
                 return $this->instance($name, $instance);
diff --git a/Spanner/src/TransactionalReadTrait.php b/Spanner/src/TransactionalReadTrait.php
index b80415e3ce8..c9b29e72a21 100644
--- a/Spanner/src/TransactionalReadTrait.php
+++ b/Spanner/src/TransactionalReadTrait.php
@@ -26,7 +26,6 @@
 trait TransactionalReadTrait
 {
     use TransactionConfigurationTrait;
-    // use RequestTrait;
 
     /**
      * @var Operation
@@ -303,15 +302,12 @@ public function execute($sql, array $options = [])
             $this->directedReadOptions ?? []
         );
 
-        if ($this->context === SessionPoolInterface::CONTEXT_READWRITE) {
-            // add LAR header
-            $options['headers']['x-goog-spanner-route-to-leader'] = ['true'];
-        }
-
         // Unsetting the internal flag
         unset($options['singleUse']);
 
-        $result = $this->operation->execute($this->session, $sql, $options);
+        $result = $this->operation->execute($this->session, $sql, $options + [
+            'route-to-leader' => $this->context === SessionPoolInterface::CONTEXT_READWRITE
+        ]);
 
         if (empty($this->id()) && $result->transaction()) {
             $this->setId($result->transaction()->id());
@@ -389,12 +385,9 @@ public function read($table, KeySet $keySet, array $columns, array $options = []
             $this->directedReadOptions ?? []
         );
 
-        if ($this->context === SessionPoolInterface::CONTEXT_READWRITE) {
-            // add LAR header
-            $options['headers']['x-goog-spanner-route-to-leader'] = ['true'];
-        }
-
-        $result = $this->operation->read($this->session, $table, $keySet, $columns, $options);
+        $result = $this->operation->read($this->session, $table, $keySet, $columns, $options + [
+            'route-to-leader' => $this->context === SessionPoolInterface::CONTEXT_READWRITE
+        ]);
         if (empty($this->id()) && $result->transaction()) {
             $this->setId($result->transaction()->id());
         }
diff --git a/Spanner/tests/Unit/DatabaseTest.php b/Spanner/tests/Unit/DatabaseTest.php
index 35d355a3fd0..99c4037f8d9 100644
--- a/Spanner/tests/Unit/DatabaseTest.php
+++ b/Spanner/tests/Unit/DatabaseTest.php
@@ -1332,9 +1332,8 @@ public function testExecute()
                 return $request->getSql() == $sql;
             }),
             Argument::that(function ($callOptions) {
-                $this->assertArrayHasKey('headers', $callOptions);
-                $this->assertArrayHasKey('x-goog-spanner-route-to-leader', $callOptions['headers']);
-                $this->assertEquals(['true'], $callOptions['headers']['x-goog-spanner-route-to-leader']);
+                $this->assertArrayHasKey('route-to-leader', $callOptions);
+                $this->assertEquals(true, $callOptions['route-to-leader']);
                 return true;
             })
         )
@@ -1428,9 +1427,8 @@ public function testExecutePartitionedUpdate()
                 return true;
             }),
             Argument::that(function ($callOptions) {
-                $this->assertArrayHasKey('headers', $callOptions);
-                $this->assertArrayHasKey('x-goog-spanner-route-to-leader', $callOptions['headers']);
-                $this->assertEquals(['true'], $callOptions['headers']['x-goog-spanner-route-to-leader']);
+                $this->assertArrayHasKey('route-to-leader', $callOptions);
+                $this->assertEquals(true, $callOptions['route-to-leader']);
                 return true;
             })
         )
diff --git a/Spanner/tests/Unit/TransactionTest.php b/Spanner/tests/Unit/TransactionTest.php
index ce4c18ad08d..bc00c7f3287 100644
--- a/Spanner/tests/Unit/TransactionTest.php
+++ b/Spanner/tests/Unit/TransactionTest.php
@@ -130,10 +130,7 @@ public function testExecute()
                 return true;
             }),
             Argument::that(function (array $callOptions) {
-                $this->assertEquals(
-                    $callOptions['headers']['x-goog-spanner-route-to-leader'],
-                    ['true']
-                );
+                $this->assertEquals($callOptions['route-to-leader'], true);
                 return true;
             })
         )
@@ -256,10 +253,7 @@ public function testExecuteUpdateBatch()
                 return true;
             }),
             Argument::that(function (array $callOptions) {
-                $this->assertEquals(
-                    $callOptions['headers']['x-goog-spanner-route-to-leader'],
-                    ['true']
-                );
+                $this->assertEquals($callOptions['route-to-leader'], true);
                 return true;
             })
         )
@@ -427,10 +421,8 @@ public function testRead()
                 return true;
             }),
             Argument::that(function (array $callOptions) {
-                $this->assertEquals(
-                    $callOptions['headers']['x-goog-spanner-route-to-leader'],
-                    ['true']
-                );
+                $this->assertArrayHasKey('route-to-leader', $callOptions);
+                $this->assertEquals(true, $callOptions['route-to-leader']);
 
                 return true;
             })