SELECT 
  a.code, 
  b.country 
FROM 
  cscart_countries as a 
  LEFT JOIN cscart_country_descriptions as b ON b.code = a.code 
  AND b.lang_code = 'ru' 
WHERE 
  1 
  AND a.status = 'A' 
ORDER BY 
  b.country

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "b.country",
      "temporary_table": {
        "table": {
          "table_name": "a",
          "access_type": "ref",
          "possible_keys": ["status"],
          "key": "status",
          "key_length": "3",
          "used_key_parts": ["status"],
          "ref": ["const"],
          "rows": 4,
          "filtered": 100,
          "index_condition": "a.`status` = 'A'"
        },
        "table": {
          "table_name": "b",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "12",
          "used_key_parts": ["code", "lang_code"],
          "ref": ["admin_test.a.code", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(b.lang_code = 'ru')"
        }
      }
    }
  }
}