diff --git a/src/judas_server/backend/backend_server.py b/src/judas_server/backend/backend_server.py
index fac89b1..6dc5c21 100644
--- a/src/judas_server/backend/backend_server.py
+++ b/src/judas_server/backend/backend_server.py
@@ -28,27 +28,6 @@ class BackendServer:
         )
         self.logger.debug("Initializing Server...")
 
-        self.known_clients: dict[str, dict[str, str | float]] = {}
-        try:
-            with open("cache/known_clients.yaml", "r") as f:
-                self.known_clients = (
-                    yaml.safe_load(f).get("known_clients", {}) or {}
-                )
-                self.logger.debug(
-                    f"Loaded known clients: {self.known_clients}"
-                )
-                self.logger.info(
-                    f"Loaded {len(self.known_clients)} known clients"
-                )
-        except FileNotFoundError:
-            self.logger.warning(
-                "known_clients.yaml not found, creating empty known clients list"
-            )
-            with open("cache/known_clients.yaml", "w") as f:
-                yaml.safe_dump({"known_clients": {}}, f)
-        except Exception as e:
-            self.logger.error(f"Error loading known clients: {e}")
-
         self.selector = selectors.DefaultSelector()
         self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         self.server_socket.setsockopt(
@@ -63,16 +42,61 @@ class BackendServer:
 
         self.clients: dict[str, Client] = {}
 
-        if self.known_clients:
-            for client_id in self.known_clients:
+        self.known_clients: dict[str, dict[str, str | float]] = (
+            self._load_known_clients()
+        )
+
+        self.running: bool = False
+
+    def _load_known_clients(self) -> dict[str, dict[str, str | float]]:
+        """Load the list of known clients from a YAML file and validate."""
+        known_clients: dict[str, dict[str, str | float]] = {}
+
+        try:
+            with open("cache/known_clients.yaml", "r") as f:
+                data = yaml.safe_load(f)
+
+                if not isinstance(data, dict):
+                    raise ValueError("YAML root must be a dict")
+
+                known_clients = data.get("known_clients", {}) or {}
+
+                if not isinstance(known_clients, dict):
+                    raise ValueError("'known_clients' must be a dict")
+
+                for client_id, client_data in known_clients.items():
+                    if not isinstance(client_data, dict):
+                        raise ValueError(
+                            f"Client {client_id} data must be a dict"
+                        )
+                    last_seen = client_data.get("last_seen", 0.0)
+                    if not isinstance(last_seen, (float, int)):
+                        raise ValueError(
+                            f"Client {client_id} 'last_seen' must be a float or int"
+                        )
+
+                self.logger.debug(f"Loaded known clients: {known_clients}")
+                self.logger.info(f"Loaded {len(known_clients)} known clients")
+
+            for client_id in known_clients:
                 client = Client(id=client_id, addr=None, socket=None)
                 client.status = ClientStatus.OFFLINE
                 client.last_seen = float(
-                    self.known_clients[client_id].get("last_seen", 0.0)
+                    known_clients[client_id].get("last_seen", 0.0)
                 )
                 self.clients[client_id] = client
 
-        self.running: bool = False
+        except FileNotFoundError:
+            self.logger.warning(
+                "known_clients.yaml not found, creating empty known clients list"
+            )
+            with open("cache/known_clients.yaml", "w") as f:
+                yaml.safe_dump({"known_clients": {}}, f)
+        except Exception as e:
+            self.logger.error(f"Error loading known clients: {e}")
+            raise
+
+        return known_clients
 
     def _save_known_clients(self) -> None:
         """Save the list of known clients to a YAML file."""