SELECT 
  a.*, 
  b.description 
FROM 
  cscart_currencies as a 
  LEFT JOIN cscart_currency_descriptions as b ON a.currency_code = b.currency_code 
  AND lang_code = 'ja' 
  INNER JOIN cscart_ult_objects_sharing ON (
    cscart_ult_objects_sharing.share_object_id = a.currency_id 
    AND cscart_ult_objects_sharing.share_company_id = 1 
    AND cscart_ult_objects_sharing.share_object_type = 'currencies'
  ) 
WHERE 
  1 
  AND status IN ('A', 'H') 
ORDER BY 
  a.position

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "ordering_operation": {
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "a",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY"
            ],
            "rows": 4,
            "filtered": 100,
            "attached_condition": "(`_testcscart`.`a`.`status` in ('A','H'))"
          }
        },
        {
          "table": {
            "table_name": "b",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "currency_code",
              "lang_code"
            ],
            "key_length": "38",
            "ref": [
              "_testcscart.a.currency_code",
              "const"
            ],
            "rows": 1,
            "filtered": 100,
            "attached_condition": "<if>(is_not_null_compl(b), (`_testcscart`.`b`.`lang_code` = 'ja'), true)"
          }
        },
        {
          "table": {
            "table_name": "cscart_ult_objects_sharing",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "share_object_id",
              "share_company_id",
              "share_object_type"
            ],
            "key_length": "159",
            "ref": [
              "_testcscart.a.currency_id",
              "const",
              "const"
            ],
            "rows": 1,
            "filtered": 100,
            "using_index": true,
            "attached_condition": "((`_testcscart`.`cscart_ult_objects_sharing`.`share_object_id` = `_testcscart`.`a`.`currency_id`) and (`_testcscart`.`cscart_ult_objects_sharing`.`share_object_type` = 'currencies'))"
          }
        }
      ]
    }
  }
}