diff --git a/amqtt/plugins/sys/broker.py b/amqtt/plugins/sys/broker.py
index b0ba07f..1ce7abe 100644
--- a/amqtt/plugins/sys/broker.py
+++ b/amqtt/plugins/sys/broker.py
@@ -42,9 +42,8 @@ STAT_START_TIME = "start_time"
 STAT_CLIENTS_MAXIMUM = "clients_maximum"
 STAT_CLIENTS_CONNECTED = "clients_connected"
 STAT_CLIENTS_DISCONNECTED = "clients_disconnected"
-MEMORY_USAGE_MAXIMUM = "memory_maximum"
-CPU_USAGE_MAXIMUM = "cpu_usage_maximum"
-CPU_USAGE_LAST = "cpu_usage_last"
+STAT_MEMORY_USAGE_MAXIMUM = "memory_maximum"
+STAT_CPU_USAGE_MAXIMUM = "cpu_usage_maximum"
 
 
 PACKET: TypeAlias = MQTTPacket[MQTTVariableHeader, MQTTPayload[MQTTVariableHeader], MQTTFixedHeader]
@@ -75,17 +74,17 @@ class BrokerSysPlugin(BasePlugin[BrokerContext]):
     def _clear_stats(self) -> None:
         """Initialize broker statistics data structures."""
         for stat in (
-            STAT_BYTES_RECEIVED,
-            STAT_BYTES_SENT,
-            STAT_MSG_RECEIVED,
-            STAT_MSG_SENT,
-            STAT_CLIENTS_MAXIMUM,
-            STAT_CLIENTS_CONNECTED,
-            STAT_CLIENTS_DISCONNECTED,
-            STAT_PUBLISH_RECEIVED,
-            STAT_PUBLISH_SENT,
-            MEMORY_USAGE_MAXIMUM,
-            CPU_USAGE_MAXIMUM
+                STAT_BYTES_RECEIVED,
+                STAT_BYTES_SENT,
+                STAT_MSG_RECEIVED,
+                STAT_MSG_SENT,
+                STAT_CLIENTS_MAXIMUM,
+                STAT_CLIENTS_CONNECTED,
+                STAT_CLIENTS_DISCONNECTED,
+                STAT_PUBLISH_RECEIVED,
+                STAT_PUBLISH_SENT,
+                STAT_MEMORY_USAGE_MAXIMUM,
+                STAT_CPU_USAGE_MAXIMUM
         ):
             self._stats[stat] = 0
 
@@ -149,14 +148,15 @@ class BrokerSysPlugin(BasePlugin[BrokerContext]):
             messages_stored += session.retained_messages_count
         messages_stored += len(self.context.retained_messages)
         subscriptions_count = sum(len(sub) for sub in self.context.subscriptions.values())
-        self._stats[STAT_CLIENTS_MAXIMUM] = client_connected
+
+        self._stats[STAT_CLIENTS_MAXIMUM] = max(self._stats[STAT_CLIENTS_MAXIMUM], client_connected)
 
         cpu_usage = self._current_process.cpu_percent(interval=0)
-        self._stats[CPU_USAGE_MAXIMUM] = max(self._stats[CPU_USAGE_MAXIMUM], cpu_usage)
+        self._stats[STAT_CPU_USAGE_MAXIMUM] = max(self._stats[STAT_CPU_USAGE_MAXIMUM], cpu_usage)
 
         mem_info_usage = self._current_process.memory_full_info()
         mem_size = mem_info_usage.rss / (1024 ** 2)
-        self._stats[MEMORY_USAGE_MAXIMUM] = max(self._stats[MEMORY_USAGE_MAXIMUM], mem_size)
+        self._stats[STAT_MEMORY_USAGE_MAXIMUM] = max(self._stats[STAT_MEMORY_USAGE_MAXIMUM], mem_size)
 
         # Broadcast updates
         tasks: deque[asyncio.Task[None]] = deque()
@@ -181,9 +181,9 @@ class BrokerSysPlugin(BasePlugin[BrokerContext]):
             "messages/retained/count": len(self.context.retained_messages),
             "messages/subscriptions/count": subscriptions_count,
             "heap/size": mem_size,
-            "heap/maximum": self._stats[MEMORY_USAGE_MAXIMUM],
+            "heap/maximum": self._stats[STAT_MEMORY_USAGE_MAXIMUM],
             "cpu/percent": cpu_usage,
-            "cpu/maximum": self._stats[CPU_USAGE_MAXIMUM],
+            "cpu/maximum": self._stats[STAT_CPU_USAGE_MAXIMUM],
         }
         for stat_name, stat_value in stats.items():
             data: bytes = val_to_bytes_str(stat_value)