diff --git a/requirement.txt b/requirement.txt
deleted file mode 100644
index 192adbd..0000000
--- a/requirement.txt
+++ /dev/null
@@ -1,23 +0,0 @@
-aiofiles==0.6.0
-aiohttp==3.7.4.post0
-aiohttp-socks==0.6.0
-async-timeout==3.0.1
-attrs==21.2.0
-chardet==4.0.0
-future==0.18.2
-h11==0.12.0
-h2==4.0.0
-hpack==4.0.0
-hyperframe==6.0.1
-idna==3.2
-jsonschema==3.2.0
-Logbook==1.5.3
-matrix-nio==0.18.7
-multidict==5.1.0
-pycryptodome==3.10.4
-pyrsistent==0.18.0
-python-socks==1.2.4
-six==1.16.0
-typing-extensions==3.10.0.2
-unpaddedbase64==2.1.0
-yarl==1.6.3
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..468ba73
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+matrix-nio==0.18.7
diff --git a/requirements_dev.txt b/requirements_dev.txt
new file mode 100644
index 0000000..b60793c
--- /dev/null
+++ b/requirements_dev.txt
@@ -0,0 +1 @@
+python-dotenv==0.19.0
diff --git a/setup.cfg b/setup.cfg
index 0baf1c8..a52660f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -12,3 +12,10 @@ python_requires = >=3.9.2
 package_dir = =src
 install_requires = 
 		matrix-nio>=0.18.7
+
+[options.extras_require]
+testing = 
+    python-dotenv>=0.19.0
+
+[options.package_data]
+matrix_bot = py.typed
diff --git a/src/matrix_bot/client.py b/src/matrix_bot/client.py
index 7fdd26d..fefa5f7 100644
--- a/src/matrix_bot/client.py
+++ b/src/matrix_bot/client.py
@@ -27,6 +27,8 @@ class Client:
     """
 
     __client: nio.AsyncClient
+    __rooms_by_aliases: dict[RoomAlias, Room]
+    __rooms_by_id: dict[RoomId, Room]
     allowed_rooms: Optional[dict[RoomId, Room]]
 
     def __init__(
@@ -50,6 +52,8 @@ class Client:
             homeserver,
             username
         )
+        self.__rooms_by_aliases = {}
+        self.__rooms_by_id = {}
         resp = loop.run_until_complete(self.__client.login(password))
         if isinstance(resp, nio.responses.LoginError):
             raise RuntimeError(f"Fail to connect: {resp.message}")
@@ -60,10 +64,7 @@ class Client:
             self.allowed_rooms = {}
             for room_name in allowed_rooms_names:
                 room = loop.run_until_complete(self.resolve_room(room_name))
-                if room.id in self.allowed_rooms:
-                    self.allowed_rooms[room.id].aliases.update(room.aliases)
-                else:
-                    self.allowed_rooms[room.id] = room
+                self.allowed_rooms[room.id] = room # room uniqueness is handled by self.resolve_room
 
 
     async def resolve_room(
@@ -72,16 +73,37 @@ class Client:
     )->Room:
         """
             Lookup a room from its id or alias.
+            If the name has already been resolved by this client, the
+            room is return directly without querying the server.
         """
+        # If the room_name is empty:
         if len(room_name) == 0:
             raise ValueError(f"Invalid room_name: {room_name}")
-        if room_name[0] == '!':
+        # If it is a known room id:
+        if room_name[0] == '!' and room_name in self.__rooms_by_id:
+            return self.__rooms_by_id[room_name]
+        # If it is a unknown room id:
+        elif room_name[0] == '!':
             return Room(id=room_name)
+        # If it is not a room id nor a room alias:
         elif room_name[0] != '#':
             raise ValueError(f"Invalid room_name: {room_name}")
+        # If it is a known room alias:
+        elif room_name in self.__rooms_by_aliases:
+            return self.__rooms_by_aliases[room_name]
+        # If it is an unknown room alias:
         else:
             resp = await self.__client.room_resolve_alias(room_name)
             if isinstance(resp, nio.responses.RoomResolveAliasError):
                 raise RuntimeError(f"Error while resolving alias: {resp.message}")
-            return Room(id=resp.room_id,aliases={room_name})
+            # If the room is already known:
+            if resp.room_id in self.__rooms_by_id:
+                room = self.__rooms_by_id[resp.room_id]
+                room.aliases.add(room_name)
+            # If the room is unknwon:
+            else:
+                room = Room(id=resp.room_id,aliases={room_name})
+                self.__rooms_by_id[resp.room_id] = room
+            self.__rooms_by_aliases[room_name] = room
+            return room
 
diff --git a/src/matrix_bot/py.typed b/src/matrix_bot/py.typed
new file mode 100644
index 0000000..e69de29