diff --git a/src/edge_proxy/environments.py b/src/edge_proxy/environments.py
index 542f9fd..8127a55 100644
--- a/src/edge_proxy/environments.py
+++ b/src/edge_proxy/environments.py
@@ -26,6 +26,8 @@
 
 logger = structlog.get_logger(__name__)
 
+SERVER_API_KEY_PREFIX = "ser."
+
 
 class EnvironmentService:
     def __init__(
@@ -77,11 +79,12 @@ def get_flags_response_data(
     ) -> dict[str, typing.Any]:
         environment_document = self.get_environment(environment_key)
         environment = EnvironmentModel.model_validate(environment_document)
+        is_server_key = environment_key.startswith(SERVER_API_KEY_PREFIX)
 
         if feature:
             feature_state = get_environment_feature_state(environment, feature)
 
-            if not filter_out_server_key_only_feature_states(
+            if not is_server_key and not filter_out_server_key_only_feature_states(
                 feature_states=[feature_state],
                 environment=environment,
             ):
@@ -90,10 +93,12 @@ def get_flags_response_data(
             data = map_feature_state_to_response_data(feature_state)
 
         else:
-            feature_states = filter_out_server_key_only_feature_states(
-                feature_states=get_environment_feature_states(environment),
-                environment=environment,
-            )
+            feature_states = get_environment_feature_states(environment)
+            if not is_server_key:
+                feature_states = filter_out_server_key_only_feature_states(
+                    feature_states=feature_states,
+                    environment=environment,
+                )
             data = map_feature_states_to_response_data(feature_states)
 
         return data
@@ -103,6 +108,8 @@ def get_identity_response_data(
     ) -> dict[str, typing.Any]:
         environment_document = self.get_environment(environment_key)
         environment = EnvironmentModel.model_validate(environment_document)
+        is_server_key = environment_key.startswith(SERVER_API_KEY_PREFIX)
+
         identity = IdentityModel.model_validate(
             self.cache.get_identity(
                 environment_api_key=environment_key,
@@ -110,14 +117,17 @@ def get_identity_response_data(
             )
         )
         trait_models = input_data.traits
-        flags = filter_out_server_key_only_feature_states(
-            feature_states=get_identity_feature_states(
-                environment,
-                identity,
-                override_traits=trait_models,
-            ),
-            environment=environment,
+        flags = get_identity_feature_states(
+            environment,
+            identity,
+            override_traits=trait_models,
         )
+
+        if not is_server_key:
+            flags = filter_out_server_key_only_feature_states(
+                feature_states=flags,
+                environment=environment,
+            )
         data = {
             "traits": map_traits_to_response_data(trait_models),
             "flags": map_feature_states_to_response_data(
diff --git a/tests/test_environments.py b/tests/test_environments.py
index 21c03ad..e9bbc88 100644
--- a/tests/test_environments.py
+++ b/tests/test_environments.py
@@ -9,7 +9,10 @@
 from pytest_mock import MockerFixture
 
 from edge_proxy.environments import EnvironmentService
-from edge_proxy.exceptions import FlagsmithUnknownKeyError
+from edge_proxy.exceptions import (
+    FeatureNotFoundError,
+    FlagsmithUnknownKeyError,
+)
 from edge_proxy.models import IdentityWithTraits
 from edge_proxy.settings import (
     EndpointCacheSettings,
@@ -230,3 +233,101 @@ async def test_get_identity_flags_response_skips_cache_for_different_identity(
     assert environment_service.get_identity_response_data.cache_info().currsize == 2
     assert environment_service.get_identity_response_data.cache_info().misses == 2
     assert environment_service.get_identity_response_data.cache_info().hits == 0
+
+
+@pytest.mark.asyncio
+async def test_get_flags_response_data_skips_filter_for_server_key(
+    mocker: MockerFixture,
+) -> None:
+    # Given
+    # We create a new settings object that contains a server key as a client_side_key
+    api_key = "ser." + environment_1_api_key
+    _settings = AppSettings(
+        environment_key_pairs=[
+            {"client_side_key": api_key, "server_side_key": "ser.key"}
+        ]
+    )
+
+    mocked_client = mocker.AsyncMock()
+    mocked_client.get.return_value = mocker.MagicMock(
+        text=orjson.dumps(environment_1), raise_for_status=lambda: None
+    )
+
+    environment_service = EnvironmentService(settings=_settings, client=mocked_client)
+    await environment_service.refresh_environment_caches()
+
+    # When
+    # We retrieve the flag response data
+    flags = environment_service.get_flags_response_data(api_key)
+    specific_flag = environment_service.get_flags_response_data(api_key, "feature_3")
+
+    # Then
+    # we get the server-side only flag
+    assert len(flags) == 3
+    assert flags[2].get("feature").get("name") == "feature_3"
+    assert specific_flag.get("feature").get("name") == "feature_3"
+
+
+@pytest.mark.asyncio
+async def test_get_flags_response_data_filters_server_side_features_for_client_key(
+    mocker: MockerFixture,
+) -> None:
+    # Given
+    # We create a new settings object that contains a client side key
+    _settings = AppSettings(
+        environment_key_pairs=[
+            {"client_side_key": environment_1_api_key, "server_side_key": "ser.key"}
+        ]
+    )
+
+    mocked_client = mocker.AsyncMock()
+    mocked_client.get.return_value = mocker.MagicMock(
+        text=orjson.dumps(environment_1), raise_for_status=lambda: None
+    )
+
+    environment_service = EnvironmentService(settings=_settings, client=mocked_client)
+    await environment_service.refresh_environment_caches()
+
+    # When
+    # We retrieve the flag response data
+    flags = environment_service.get_flags_response_data(environment_1_api_key)
+    with pytest.raises(FeatureNotFoundError):
+        environment_service.get_flags_response_data(environment_1_api_key, "feature_3")
+
+    # Then
+    # we only get the two client side flags
+    assert len(flags) == 2
+
+
+@pytest.mark.asyncio
+async def test_get_identity_flags_response_skips_filter_for_server_key(
+    mocker: MockerFixture,
+) -> None:
+    # Given
+    # We create a new settings object that contains a server key as a client_side_key
+    api_key = "ser." + environment_1_api_key
+    _settings = AppSettings(
+        environment_key_pairs=[
+            {"client_side_key": api_key, "server_side_key": "ser.key"}
+        ]
+    )
+
+    mocked_client = mocker.AsyncMock()
+    mocked_client.get.return_value = mocker.MagicMock(
+        text=orjson.dumps(environment_1), raise_for_status=lambda: None
+    )
+
+    environment_service = EnvironmentService(settings=_settings, client=mocked_client)
+    await environment_service.refresh_environment_caches()
+
+    # When
+    # We retrieve the flags for an identity
+    result = environment_service.get_identity_response_data(
+        IdentityWithTraits(identifier="foo"), api_key
+    )
+
+    # Then
+    # we get the server-side only flag
+    flags = result.get("flags")
+    assert len(flags) == 3
+    assert flags[2].get("feature").get("name") == "feature_3"