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 = 'uk' 
WHERE 
  1 
  AND a.status = 'A' 
ORDER BY 
  b.country

Query time 0.00111

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "b.country",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "a",
              "access_type": "ref",
              "possible_keys": ["status"],
              "key": "status",
              "key_length": "3",
              "used_key_parts": ["status"],
              "ref": ["const"],
              "rows": 251,
              "filtered": 100,
              "attached_condition": "a.`status` = 'A'",
              "using_index": true
            }
          },
          {
            "table": {
              "table_name": "b",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY"],
              "key": "PRIMARY",
              "key_length": "12",
              "used_key_parts": ["code", "lang_code"],
              "ref": ["lillyshop_lillyshop.a.code", "const"],
              "rows": 1,
              "filtered": 100,
              "attached_condition": "trigcond(b.lang_code = 'uk')"
            }
          }
        ]
      }
    }
  }
}