diff --git a/composer.json b/composer.json
index 79d2d6c9..a9bba45b 100644
--- a/composer.json
+++ b/composer.json
@@ -67,6 +67,7 @@
                 "web-root": "web/"
             },
             "file-mapping": {
+                "[web-root]/.eslintrc.json": false,
                 "[web-root]/sites/development.services.yml": false
             }
         },
diff --git a/web/sites/default/settings.php b/web/sites/default/settings.php
index 63df8b09..7be88604 100644
--- a/web/sites/default/settings.php
+++ b/web/sites/default/settings.php
@@ -16,6 +16,9 @@
   'host' => getenv('DB_HOST'),
   'port' => '3306',
   'driver' => 'mysql',
+  // Drupal's recommended isolation level. Avoids gap-lock deadlocks on
+  // concurrent writes, and matches the Silta MariaDB config.
+  'isolation_level' => 'READ COMMITTED',
 ];
 
 // Salt for one-time login links, cancel links, form tokens, etc.