Timestamps are being stored as Longs in hbase by the HBaseTimelineWriterImpl code. There seem to be some places in the code where there are conversions between Long to byte to String for easier argument passing between function calls. Then these values end up being converted back to byte while storing in hbase.
It would be better to pass around byte or the Longs themselves as applicable.
This may result in some api changes (store function) as well in adding a few more function calls like getColumnQualifier which accepts a pre-encoded byte array. It will be in addition to the existing api which accepts a String and the ColumnHelper to return a byte column name instead of a String one.
Filing jira to track these changes.