Search code examples
azureazure-cosmosdbazure-log-analytics

How to optimize RUs for Replace of a document in Azure Cosmos DB?

I'm a beginner to Azure. I'm using log monitors to view the logs for a Cosmos DB resource. I could see one log with Replace operation which is consuming a lot of average RUs.

Generally operation names should be CREATE/DELETE/UPDATE/READ . But why REPLACE operation has come in place over here - I could not understand it. And why the REPLACE operation is consuming lot of RUs?

What can I try next?

enter image description here

Solution

  • Updates in Cosmos are full replacement operations rather than in-place updates, as such these consume more RU/s than inserts. Also, the larger the document, the more throughput required for the update.

    Strategies to optimize throughput consumption on update operations typically center around splitting documents into two with properties that don't change going into one document that is typically larger and another document with those properties that change frequently going into an other that is smaller. This will allow for the updates to be made on a smaller document which reduces RU/s consumed to do the operation.

    All that said, 12 RU/s is not an inordinate amount of RU/s for a replace operation. I don't think you will get much, if any throughput reduction doing this. But you can certainly try.