From the CosmosDB documentation on Request Units:
The cost to do a point read (fetching a single item by its ID and partition key value) for a 1-KB item is one Request Unit (or one RU).
Is 1 RU an absolute minimum? What would be the cost of e.g., a 0.5-KB document point-read?
Is 1 RU an absolute minimum? What would be the cost of e.g., a 0.5-KB document point-read?
Yes. I ran a very simple test with a document which is less than 1KB in size and noticed the RU charge for point read. The RU charge was 1 for that operation.