diff --git a/fastapi_cache/__init__.py b/fastapi_cache/__init__.py
index e21e4b7..e9ef55e 100644
--- a/fastapi_cache/__init__.py
+++ b/fastapi_cache/__init__.py
@@ -1,9 +1,8 @@
 from typing import ClassVar, Optional, Type
 
-from fastapi_cache.backends import Backend
 from fastapi_cache.coder import Coder, JsonCoder
 from fastapi_cache.key_builder import default_key_builder
-from fastapi_cache.types import KeyBuilder
+from fastapi_cache.types import Backend, KeyBuilder
 
 
 __all__ = [
diff --git a/fastapi_cache/backends/__init__.py b/fastapi_cache/backends/__init__.py
index 4519aa9..261af6c 100644
--- a/fastapi_cache/backends/__init__.py
+++ b/fastapi_cache/backends/__init__.py
@@ -1,20 +1,29 @@
-import abc
-from typing import Optional, Tuple
+from fastapi_cache.types import Backend
+from fastapi_cache.backends import inmemory
 
 
-class Backend:
-    @abc.abstractmethod
-    async def get_with_ttl(self, key: str) -> Tuple[int, Optional[bytes]]:
-        raise NotImplementedError
+__all__ = ["Backend", "inmemory"]
 
-    @abc.abstractmethod
-    async def get(self, key: str) -> Optional[bytes]:
-        raise NotImplementedError
+# import each backend in turn and add to __all__. This syntax
+# is explicitly supported by type checkers, while more dynamic
+# syntax would not be recognised.
+try:
+    from fastapi_cache.backends import dynamodb
+except ImportError:
+    pass
+else:
+    __all__ += ["dynamodb"]
 
-    @abc.abstractmethod
-    async def set(self, key: str, value: bytes, expire: Optional[int] = None) -> None:
-        raise NotImplementedError
+try:
+    from fastapi_cache.backends import memcached
+except ImportError:
+    pass
+else:
+    __all__ += ["memcached"]
 
-    @abc.abstractmethod
-    async def clear(self, namespace: Optional[str] = None, key: Optional[str] = None) -> int:
-        raise NotImplementedError
+try:
+    from fastapi_cache.backends import redis
+except ImportError:
+    pass
+else:
+    __all__ += ["redis"]
diff --git a/fastapi_cache/backends/dynamodb.py b/fastapi_cache/backends/dynamodb.py
index 94318c9..ec639d1 100644
--- a/fastapi_cache/backends/dynamodb.py
+++ b/fastapi_cache/backends/dynamodb.py
@@ -4,7 +4,7 @@ from typing import TYPE_CHECKING, Optional, Tuple
 from aiobotocore.client import AioBaseClient
 from aiobotocore.session import AioSession, get_session
 
-from fastapi_cache.backends import Backend
+from fastapi_cache.types import Backend
 
 if TYPE_CHECKING:
     from types_aiobotocore_dynamodb import DynamoDBClient
diff --git a/fastapi_cache/backends/inmemory.py b/fastapi_cache/backends/inmemory.py
index 219dd25..5ef101b 100644
--- a/fastapi_cache/backends/inmemory.py
+++ b/fastapi_cache/backends/inmemory.py
@@ -3,7 +3,7 @@ from asyncio import Lock
 from dataclasses import dataclass
 from typing import Dict, Optional, Tuple
 
-from fastapi_cache.backends import Backend
+from fastapi_cache.types import Backend
 
 
 @dataclass
diff --git a/fastapi_cache/backends/memcached.py b/fastapi_cache/backends/memcached.py
index 22e201f..156a3e6 100644
--- a/fastapi_cache/backends/memcached.py
+++ b/fastapi_cache/backends/memcached.py
@@ -2,7 +2,7 @@ from typing import Optional, Tuple
 
 from aiomcache import Client
 
-from fastapi_cache.backends import Backend
+from fastapi_cache.types import Backend
 
 
 class MemcachedBackend(Backend):
diff --git a/fastapi_cache/backends/redis.py b/fastapi_cache/backends/redis.py
index 22a63ef..5eef48f 100644
--- a/fastapi_cache/backends/redis.py
+++ b/fastapi_cache/backends/redis.py
@@ -3,11 +3,11 @@ from typing import Optional, Tuple, Union
 from redis.asyncio.client import Redis
 from redis.asyncio.cluster import RedisCluster
 
-from fastapi_cache.backends import Backend
+from fastapi_cache.types import Backend
 
 
 class RedisBackend(Backend):
-    def __init__(self, redis: Union[Redis[bytes], RedisCluster[bytes]]):
+    def __init__(self, redis: Union["Redis[bytes]", "RedisCluster[bytes]"]):
         self.redis = redis
         self.is_cluster: bool = isinstance(redis, RedisCluster)
 
diff --git a/fastapi_cache/types.py b/fastapi_cache/types.py
index 63192ab..1ae4069 100644
--- a/fastapi_cache/types.py
+++ b/fastapi_cache/types.py
@@ -1,3 +1,4 @@
+import abc
 from typing import Any, Awaitable, Callable, Dict, Optional, Tuple, Union
 
 from starlette.requests import Request
@@ -20,3 +21,21 @@ class KeyBuilder(Protocol):
         kwargs: Dict[str, Any],
     ) -> Union[Awaitable[str], str]:
         ...
+
+
+class Backend(abc.ABC):
+    @abc.abstractmethod
+    async def get_with_ttl(self, key: str) -> Tuple[int, Optional[bytes]]:
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    async def get(self, key: str) -> Optional[bytes]:
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    async def set(self, key: str, value: bytes, expire: Optional[int] = None) -> None:
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    async def clear(self, namespace: Optional[str] = None, key: Optional[str] = None) -> int:
+        raise NotImplementedError