diff --git a/src/amplitude/client.py b/src/amplitude/client.py
index dded59f..d028587 100644
--- a/src/amplitude/client.py
+++ b/src/amplitude/client.py
@@ -37,7 +37,7 @@ class Amplitude:
         shutdown(): Shutdown the client instance
     """
 
-    def __init__(self, api_key: str, configuration: Config = Config()):
+    def __init__(self, api_key: str, configuration: Optional[Config] = None):
         """The constructor for the Amplitude class
 
         Args:
@@ -45,7 +45,7 @@ def __init__(self, api_key: str, configuration: Config = Config()):
             configuration (amplitude.config.Config, optional): The configuration of client instance. A new instance
                 with default config value will be used by default.
         """
-        self.configuration: Config = configuration
+        self.configuration: Config = configuration or Config()
         self.configuration.api_key = api_key
         self.__timeline = Timeline()
         self.__timeline.setup(self)
diff --git a/src/amplitude/config.py b/src/amplitude/config.py
index 1674bca..78fa2db 100644
--- a/src/amplitude/config.py
+++ b/src/amplitude/config.py
@@ -55,7 +55,7 @@ def __init__(self, api_key: str = None,
                  server_zone: str = constants.DEFAULT_ZONE,
                  use_batch: bool = False,
                  server_url: Optional[str] = None,
-                 storage_provider: StorageProvider = InMemoryStorageProvider(),
+                 storage_provider: Optional[StorageProvider] = None,
                  plan: Plan = None,
                  ingestion_metadata: IngestionMetadata = None):
         """The constructor of Config class"""
@@ -70,7 +70,7 @@ def __init__(self, api_key: str = None,
         self.server_zone: str = server_zone
         self.use_batch: bool = use_batch
         self._url: Optional[str] = server_url
-        self.storage_provider: StorageProvider = storage_provider
+        self.storage_provider: StorageProvider = storage_provider or InMemoryStorageProvider()
         self.opt_out: bool = False
         self.plan: Plan = plan
         self.ingestion_metadata: IngestionMetadata = ingestion_metadata
diff --git a/src/test/test_client.py b/src/test/test_client.py
index 56ae886..6301572 100644
--- a/src/test/test_client.py
+++ b/src/test/test_client.py
@@ -16,6 +16,13 @@ def setUp(self) -> None:
 
     def tearDown(self) -> None:
         self.client.shutdown()
+    
+    def test_amplitude_client_init_multiple_instance(self):
+        #  test multiple instance inited with different API keys
+        client1 = Amplitude(api_key="test api key 1")
+        client2 = Amplitude(api_key="test api key 2")
+        self.assertNotEqual(client1.configuration.api_key, client2.configuration.api_key)
+        self.assertNotEqual(client1.configuration.storage_provider, client2.configuration.storage_provider)
 
     def test_amplitude_client_track_success(self):
         post_method = MagicMock()
diff --git a/src/test/test_config.py b/src/test/test_config.py
index 9217bcb..3576e96 100644
--- a/src/test/test_config.py
+++ b/src/test/test_config.py
@@ -120,7 +120,11 @@ def test_config_flush_queue_size_decrease_no_less_than_one(self):
         self.assertEqual(1, config.flush_queue_size)
         config._increase_flush_divider()
         self.assertEqual(1, config.flush_queue_size)
-
+    
+    def test_config_multiple_instances_has_different_storage_provider(self):
+        config1 = Config()
+        config2 = Config()
+        self.assertIsNot(config1.storage_provider, config2.storage_provider)
 
 if __name__ == '__main__':
     unittest.main()