diff --git a/moto/apigateway/models.py b/moto/apigateway/models.py
index b6a515bfb75f..51712e30a2ef 100644
--- a/moto/apigateway/models.py
+++ b/moto/apigateway/models.py
@@ -1166,7 +1166,10 @@ def create_from_cloudformation_json(  # type: ignore[misc]
 
     def add_child(self, path: str, parent_id: Optional[str] = None) -> Resource:
         child_id = create_apigw_id(
-            self.account_id, self.region_name, "resource", parent_id + "." + path
+            self.account_id,
+            self.region_name,
+            "resource",
+            (parent_id or "") + "." + path,
         )
         child = Resource(
             resource_id=child_id,
@@ -2158,7 +2161,7 @@ def create_api_key(self, payload: Dict[str, Any]) -> ApiKey:
                 if api_key.value == payload["value"]:
                     raise ApiKeyAlreadyExists()
         api_key_id = create_apigw_id(
-            self.account_id, self.region_name, "api_key", payload.get("name")
+            self.account_id, self.region_name, "api_key", payload["name"]
         )
         key = ApiKey(api_key_id=api_key_id, **payload)
         self.keys[key.id] = key
diff --git a/moto/apigateway/utils.py b/moto/apigateway/utils.py
index 661317c0a163..9707a60b2a86 100644
--- a/moto/apigateway/utils.py
+++ b/moto/apigateway/utils.py
@@ -8,7 +8,7 @@
 from moto.utilities.id_generator import generate_str_id
 
 
-def create_apigw_id(account_id, region, resource, name) -> str:
+def create_apigw_id(account_id: str, region: str, resource: str, name: str) -> str:
     return generate_str_id(
         account_id,
         region,
diff --git a/moto/utilities/id_generator.py b/moto/utilities/id_generator.py
index 8d376ee02f0f..8a59f9ab5377 100644
--- a/moto/utilities/id_generator.py
+++ b/moto/utilities/id_generator.py
@@ -1,5 +1,5 @@
 import threading
-from typing import Callable
+from typing import Any, Callable
 
 from moto.moto_api._internal import mock_random
 
@@ -11,38 +11,50 @@ class MotoIdManager:
     use the `id_manager` instance created below."""
 
     _custom_ids: dict[str, str]
-    _id_sources: [IdSource]
+    _id_sources: list[IdSource]
 
     _lock: threading.RLock
 
-    def __init__(self):
+    def __init__(self) -> None:
         self._custom_ids = {}
         self._lock = threading.RLock()
         self._id_sources = []
 
         self.add_id_source(self.get_custom_id)
 
-    def get_custom_id(self, account_id, region, service, resource, name) -> str | None:
+    def get_custom_id(
+        self, account_id: str, region: str, service: str, resource: str, name: str
+    ) -> str | None:
         # retrieves a custom_id for a resource. Returns None
         return self._custom_ids.get(
             ".".join([account_id, region, service, resource, name])
         )
 
-    def set_custom_id(self, account_id, region, service, resource, name, custom_id):
+    def set_custom_id(
+        self,
+        account_id: str,
+        region: str,
+        service: str,
+        resource: str,
+        name: str,
+        custom_id: str,
+    ) -> None:
         # sets a custom_id for a resource
         with self._lock:
             self._custom_ids[
                 ".".join([account_id, region, service, resource, name])
             ] = custom_id
 
-    def unset_custom_id(self, account_id, region, service, resource, name):
+    def unset_custom_id(
+        self, account_id: str, region: str, service: str, resource: str, name: str
+    ) -> None:
         # removes a set custom_id for a resource
         with self._lock:
             self._custom_ids.pop(
                 ".".join([account_id, region, service, resource, name]), None
             )
 
-    def add_id_source(self, id_source: IdSource):
+    def add_id_source(self, id_source: IdSource) -> None:
         self._id_sources.append(id_source)
 
     def find_id_from_sources(
@@ -51,14 +63,22 @@ def find_id_from_sources(
         for id_source in self._id_sources:
             if found_id := id_source(account_id, region, service, resource, name):
                 return found_id
+        return None
 
 
 id_manager = MotoIdManager()
 
 
-def moto_id(fn):
+def moto_id(fn: Callable[..., str]) -> Callable[..., str]:
     # Decorator for helping in creation of static ids within Moto.
-    def _wrapper(account_id, region, service, resource, name, **kwargs):
+    def _wrapper(
+        account_id: str,
+        region: str,
+        service: str,
+        resource: str,
+        name: str,
+        **kwargs: dict[str, Any],
+    ) -> str:
         if found_id := id_manager.find_id_from_sources(
             account_id, region, service, resource, name
         ):
@@ -69,14 +89,14 @@ def _wrapper(account_id, region, service, resource, name, **kwargs):
 
 
 @moto_id
-def generate_str_id(
-    account_id,
-    region,
-    service,
-    resource,
-    name,
+def generate_str_id(  # type: ignore
+    account_id: str,
+    region: str,
+    service: str,
+    resource: str,
+    name: str,
     length: int = 20,
     include_digits: bool = True,
     lower_case: bool = False,
-):
+) -> str:
     return mock_random.get_random_string(length, include_digits, lower_case)