diff --git a/lib/private/AppConfig.php b/lib/private/AppConfig.php
index 0887a41b2d0a8..d3c7efcf39b70 100644
--- a/lib/private/AppConfig.php
+++ b/lib/private/AppConfig.php
@@ -58,6 +58,7 @@ class AppConfig implements IAppConfig {
 	private const int ENCRYPTION_PREFIX_LENGTH = 21; // strlen(self::ENCRYPTION_PREFIX)
 	private const string LOCAL_CACHE_KEY = 'OC\\AppConfig';
 	private const int LOCAL_CACHE_TTL = 3;
+	private const int MAX_NON_LAZY_SIZE = 128; // bytes
 
 	/** @var array<string, array<string, string>> ['app_id' => ['config_key' => 'config_value']] */
 	private array $fastCache = [];   // cache for normal config keys
@@ -856,6 +857,17 @@ private function setTypedValue(
 			$value = self::ENCRYPTION_PREFIX . $this->crypto->encrypt($value);
 		}
 
+		if (!$lazy && strlen($value) > self::MAX_NON_LAZY_SIZE) {
+			$this->logger->error(
+				'[Deprecated] App config {app}:{key} is larger than {maxSize} bytes. It should be declared as lazy.',
+				[
+					'app' => $app,
+					'key' => $key,
+					'maxSize' => self::MAX_NON_LAZY_SIZE,
+				]
+			);
+		}
+
 		if ($this->hasKey($app, $key, $lazy)) {
 			/**
 			 * no update if key is already known with set lazy status and value is
diff --git a/lib/private/Config/UserConfig.php b/lib/private/Config/UserConfig.php
index 2869b590f5e0a..e884b96029d94 100644
--- a/lib/private/Config/UserConfig.php
+++ b/lib/private/Config/UserConfig.php
@@ -55,6 +55,7 @@ class UserConfig implements IUserConfig {
 	private const int APP_MAX_LENGTH = 32;
 	private const int KEY_MAX_LENGTH = 64;
 	private const int INDEX_MAX_LENGTH = 64;
+	private const int MAX_NON_LAZY_SIZE = 128; // bytes
 
 	/** @var CappedMemoryCache<array<string, array<string, UserConfigEntry>>>  cache for normal config keys */
 	private CappedMemoryCache $fastCache;
@@ -1153,6 +1154,17 @@ private function setTypedValue(
 			return false;
 		}
 		$this->loadConfig($userId, $lazy);
+		if (!$lazy && strlen($value) > self::MAX_NON_LAZY_SIZE) {
+			$this->logger->error(
+				'[Deprecated] User {userId} config "{app}:{key}" is larger than {maxSize} bytes. It should be declared as lazy.',
+				[
+					'app' => $app,
+					'key' => $key,
+					'userId' => $userId,
+					'maxSize' => self::MAX_NON_LAZY_SIZE,
+				]
+			);
+		}
 
 		$inserted = $refreshCache = false;
 		$origValue = $value;