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 0.00407

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.40"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_mailing_lists",
          "access_type": "ALL",
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "1.00",
            "eval_cost": "0.20",
            "prefix_cost": "1.20",
            "data_read_per_join": "792"
          },
          "used_columns": [
            "list_id",
            "timestamp",
            "from_email",
            "from_name",
            "reply_to",
            "show_on_checkout",
            "show_on_registration",
            "status",
            "register_autoresponder"
          ],
          "attached_condition": "(`twebezli_Commercemodalpopup`.`cscart_mailing_lists`.`status` = 'A')"
        }
      },
      {
        "table": {
          "table_name": "cscart_common_descriptions",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "object_id",
            "lang_code",
            "object_holder"
          ],
          "key_length": "108",
          "ref": [
            "twebezli_Commercemodalpopup.cscart_mailing_lists.list_id",
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "1.00",
            "eval_cost": "0.20",
            "prefix_cost": "2.40",
            "data_read_per_join": "608"
          },
          "used_columns": [
            "object_id",
            "object_type",
            "description",
            "lang_code",
            "object",
            "object_holder"
          ],
          "attached_condition": "<if>(is_not_null_compl(cscart_common_descriptions), (`twebezli_Commercemodalpopup`.`cscart_common_descriptions`.`object_id` = `twebezli_Commercemodalpopup`.`cscart_mailing_lists`.`list_id`), true)"
        }
      }
    ]
  }
}