I am sending some IoT events into Azure Cosmos DB. I am partitioning by device id and I am always querying by device id. I want to know if the automatically created indexes are separated by partition key. Specifically if I do query like
SELECT TOP 5 ... FROM events WHERE deviceId = X ORDER BY timeStamp DESC
Will it use the automatically created index on timeStamp and if so is it effective. Basically what I am asking is if there are separate indexes on timeStamp for each partition key (deviceId in my case) because otherwise the index will be relatively useless because the range will contain a lot of irrelevant data from other devices. If this was SQL Server I would create an index on deviceId followed by timeStamp but I am not sure how Cosmos DB works by default.