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 = 'ru' 
  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 0.00066

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "9.65"
    },
    "ordering_operation": {
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "2.00"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "a",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY"
            ],
            "rows_examined_per_scan": 4,
            "rows_produced_per_join": 2,
            "filtered": "50.00",
            "cost_info": {
              "read_cost": "2.45",
              "eval_cost": "0.40",
              "prefix_cost": "2.85",
              "data_read_per_join": "208"
            },
            "used_columns": [
              "currency_id",
              "currency_code",
              "after",
              "symbol",
              "coefficient",
              "is_primary",
              "position",
              "decimals_separator",
              "thousands_separator",
              "decimals",
              "status"
            ],
            "attached_condition": "(`db_emaika1`.`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": [
              "db_emaika1.a.currency_code",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "2.00",
              "eval_cost": "0.40",
              "prefix_cost": "5.25",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "currency_code",
              "description",
              "lang_code"
            ]
          }
        },
        {
          "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": [
              "db_emaika1.a.currency_id",
              "const",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "2.00",
              "eval_cost": "0.40",
              "prefix_cost": "7.65",
              "data_read_per_join": "320"
            },
            "used_columns": [
              "share_company_id",
              "share_object_id",
              "share_object_type"
            ],
            "attached_condition": "(`db_emaika1`.`cscart_ult_objects_sharing`.`share_object_id` = `db_emaika1`.`a`.`currency_id`)"
          }
        }
      ]
    }
  }
}