Analytics storage uses Column Store format to save your data. This means data is written to disk column by column rather than row by row. This makes all aggregation function run fast because disk does not need to work hard to find data row by row anymore. Cosmos DB takes responsibility to move data from Transaction Store to Analytical Store too. You do not need to write any ETL packages to accomplish this. That means you do not need to figure out which data needs to update, which data should be deleted. Azure Cosmos DB figures all data for you, syncs the data between these two storage engines. This gives us the isolation we have been looking for between transactional and analytical environments. Data written to transactional storage will be available in Analytical Storage less than 5 minutes. In my experience, it really depends on the size of the database, if you have a smaller database usually data becomes available in Analytical Storage in less than a minute.
This makes the data easy to ingest into Azure Synapse Analytics, for example.