diff --git a/source/packages/plg_system_mokosuitebeauty/src/Helper/BookingHelper.php b/source/packages/plg_system_mokosuitebeauty/src/Helper/BookingHelper.php
index 6a3a447..dcc34ca 100644
--- a/source/packages/plg_system_mokosuitebeauty/src/Helper/BookingHelper.php
+++ b/source/packages/plg_system_mokosuitebeauty/src/Helper/BookingHelper.php
@@ -82,18 +82,52 @@ class BookingHelper
 	{
 		$db = Factory::getContainer()->get(DatabaseInterface::class);
 
-		$booking = (object) [
-			'client_contact_id' => $clientContactId,
-			'stylist_id'        => $stylistId,
-			'service_id'        => $serviceId,
-			'start_time'        => $datetime,
-			'status'            => 'confirmed',
-			'created_at'        => Factory::getDate()->toSql(),
-		];
+		// Get service duration for overlap check
+		$db->setQuery($db->getQuery(true)->select('duration_minutes')->from('#__mokosuitebeauty_services')->where('id = ' . (int) $serviceId));
+		$duration = (int) $db->loadResult();
 
-		$db->insertObject('#__mokosuitebeauty_bookings', $booking, 'id');
+		if ($duration <= 0) {
+			return (object) ['success' => false, 'error' => 'Invalid service'];
+		}
 
-		return (object) ['success' => true, 'booking_id' => (int) $booking->id];
+		$db->transactionStart();
+
+		try {
+			// Check for overlapping bookings with row lock
+			$db->setQuery(
+				'SELECT COUNT(*) FROM #__mokosuitebeauty_bookings b'
+				. ' JOIN #__mokosuitebeauty_services s ON s.id = b.service_id'
+				. ' WHERE b.stylist_id = ' . (int) $stylistId
+				. ' AND b.status NOT IN (' . $db->quote('cancelled') . ',' . $db->quote('no_show') . ')'
+				. ' AND b.start_time < DATE_ADD(' . $db->quote($datetime) . ', INTERVAL ' . $duration . ' MINUTE)'
+				. ' AND DATE_ADD(b.start_time, INTERVAL s.duration_minutes MINUTE) > ' . $db->quote($datetime)
+				. ' FOR UPDATE'
+			);
+			$conflicts = (int) $db->loadResult();
+
+			if ($conflicts > 0) {
+				$db->transactionRollback();
+				return (object) ['success' => false, 'error' => 'Time slot is no longer available'];
+			}
+
+			$booking = (object) [
+				'client_contact_id' => $clientContactId,
+				'stylist_id'        => $stylistId,
+				'service_id'        => $serviceId,
+				'start_time'        => $datetime,
+				'status'            => 'confirmed',
+				'created_at'        => Factory::getDate()->toSql(),
+			];
+
+			$db->insertObject('#__mokosuitebeauty_bookings', $booking, 'id');
+
+			$db->transactionCommit();
+
+			return (object) ['success' => true, 'booking_id' => (int) $booking->id];
+		} catch (\Throwable $e) {
+			$db->transactionRollback();
+			return (object) ['success' => false, 'error' => 'Booking failed'];
+		}
 	}
 
 	/**
diff --git a/source/packages/plg_system_mokosuitebeauty/src/Helper/WalkInHelper.php b/source/packages/plg_system_mokosuitebeauty/src/Helper/WalkInHelper.php
index 939c205..d194ca6 100644
--- a/source/packages/plg_system_mokosuitebeauty/src/Helper/WalkInHelper.php
+++ b/source/packages/plg_system_mokosuitebeauty/src/Helper/WalkInHelper.php
@@ -77,7 +77,7 @@ class WalkInHelper
 			->select('COALESCE(SUM(s.duration_minutes), 0)')
 			->from($db->quoteName('#__mokosuitebeauty_walkins', 'w'))
 			->join('LEFT', $db->quoteName('#__mokosuitebeauty_services', 's') . ' ON s.id = w.service_id')
-			->where($db->quoteName('w.status') . ' IN (' . $db->quote('waiting') . ',' . $db->quote('in_service') . ')'));
+			->where($db->quoteName('w.status') . ' = ' . $db->quote('waiting')));
 
 		$totalMinutes = (int) $db->loadResult();