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 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "const_condition": "1",
    "table": {
      "table_name": "cscart_mailing_lists",
      "access_type": "system",
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_common_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "108",
      "used_key_parts": ["object_id", "lang_code", "object_holder"],
      "ref": ["const", "const", "const"],
      "rows": 1,
      "filtered": 100
    }
  }
}