SELECT 
  * 
FROM 
  cscart_mailing_lists 
  LEFT JOIN cscart_common_descriptions ON cscart_common_descriptions.object_id = cscart_mailing_lists.list_id 
  AND cscart_common_descriptions.object_holder = 'mailing_lists' 
  AND cscart_common_descriptions.lang_code = 'en' 
WHERE 
  1 
  AND cscart_mailing_lists.status = 'A'

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.01273144,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_mailing_lists",
          "access_type": "ALL",
          "loops": 1,
          "rows": 1,
          "cost": 0.0110178,
          "filtered": 100,
          "attached_condition": "cscart_mailing_lists.`status` = 'A'"
        }
      },
      {
        "table": {
          "table_name": "cscart_common_descriptions",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "108",
          "used_key_parts": ["object_id", "lang_code", "object_holder"],
          "ref": [
            "u985510652_ecartify.cscart_mailing_lists.list_id",
            "const",
            "const"
          ],
          "loops": 1,
          "rows": 1,
          "cost": 0.00171364,
          "filtered": 100,
          "attached_condition": "trigcond(cscart_common_descriptions.object_id = cscart_mailing_lists.list_id and cscart_common_descriptions.object_holder = 'mailing_lists' and cscart_common_descriptions.lang_code = 'en')"
        }
      }
    ]
  }
}