I am trying to optimize my usage of Request Units. Say in a span of one minute, is it better to upload 10 0.1MB documents or a single 1MB document? I heard that if the total amount of data is the same, then the RU usage would be the same, but it makes sense to me that if I access the database to write to it more frequently then it would be more costly in terms of RUs.
Thanks.
The RU calculation is based on a variety of factors one of which is document size. Right now you're trying to do micro optimizations on RU when you should be designing based on your read/write patterns and ensuring that you can efficiently access the data you need. The difference between 10*0.1 and 1.0 in this case should take a backseat as the RU cost difference will be negligible.
Azure CosmosDB - Most efficient way to upload documents (size, frequency)