[IOT Lab] Suggestion: More info about RUs

[deborahc]

Section: https://github.com/AzureCosmosDB/scenario-based-labs/blob/master/IoT/HOL%20step-by%20step%20-%20Cosmos%20DB%20scenario-based%20labs%20-%20IoT.md#about-cosmos-db-throughput

In this section, it'd be great to add something at the end along the lines of:

• Cosmos DB returns the RU charge of every operation, accessible via the Portal (for queries) or SDK. With this information, you can estimate the total RU/s required for your workload by multiplying the number operations (reads, writes, or queries) per second required by the RU charge of each operation.

Cosmos DB allows you to increment/decrement the RUs in small increments of 100 at the database level, or at the container level. It is recommended that you configure throughput at the container granularity for guaranteed performance for the container all the time, backed by SLAs. Other guarantees that Cosmos DB delivers are 99.999% read and write availability all around the world, with those reads and writes being served in less than 10 milliseconds at the 99th percentile.