how do I figure out provisional throughput for AWS DynamoDB table?

Question

My system is supposed to write a large amount of data into a DynamoDB table every day. These writes come in bursts, i.e. at certain times each day several different processes have to dump their output data into the same table. Speed of writing is not critical as long as all the daily data gets written before the next dump occurs. I need to figure out the right way of calculating the provisional capacity for my table.

So for simplicity let's assume that I have only one process writing data once a day and it has to write upto X items into the table (each item < 1KB). Is the capacity I would have to specify essentially equal to X / 24 / 3600 writes/second?

Thx

Answer 1

The provisioned capacity is in terms of writes/second. You need to make sure that you can handle the PEAK number of writes/second that you are going to expect, not the average over the day. So, if you have a single process that runs once a day and makes X number of writes, of Y size (in KB, rounded up), over Z number of seconds, your formula would be

capacity = (X * Y) / Z

So, say you had 100K writes over 100 seconds and each write < 1KB, you would need 1000 w/s capacity.

Note that in order to minimize provisioned write capacity needs, it is best to add data into the system on a more continuous basis, so as to reduce peaks in necessary read/write capacity.