public static String rangeKey(long value) {
    return encodeBase62(value, true);
  }
@Test
  public void testRangeKey() {
    Assert.assertEquals("44C92", IdHelper.rangeKey(1000000L));
    Assert.assertEquals("71l9Zo9o", IdHelper.rangeKey(100000000000L));
    Assert.assertTrue(IdHelper.rangeKey(1000000L).compareTo(IdHelper.rangeKey(100000000000L)) < 0);
  }