Bigtable now supports Aggregate Values at Write Time which can perform operations like SUM natively within a row. Instead of providing a new value for a row/column/timestamp, you provide a delta to incorporate into the existing total.

Time bucketing is completely user controlled. For example, when writing to a column in a SUM column family you can produce an hourly sum by picking a timestamp like TIMESTAMP_TRUNC(HOURS, now()) with your client language's time library. You can also atomically update multiple columns with different granularity in the same row, e.g. one column for per-minute sums, another for per-hour, per-day, etc.