Upserts in HBase
The answer is ☞ HTable.incrementColumnValue:
This method increments a column value by a given amount. If the row and column does not exist, the row and the column will be added and the amount specified will be added to zero. This method is very useful because it essentially does one read and one write without you having to make two calls to HBase. It reads the existing value, updates it to a new value and returns back the updated value.
Upserts (atomic, in-place updates) is one of the most appreciated features in MongoDB, so now you know how to do that with HBase.