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Deploying a 100% DirectQuery application is a valid use case, however often it can be a good idea to put part of the granular data in-memory. This page explains when and how.

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Hybrid distributed mode

A classic use case for DirectQuery is giving access to the historical data of an in-memory Atoti application. Historical data may be too large to fit entirely in-memory or too costly for “cold” data that users rarely access. For that, it is possible to have Atoti DirectQuery nodes alongside Atoti in-memory nodes in a Distributed set-up and expose it in a unified and consistent data model to the end users.
DirectQuery hybrid distributed model
Note that you don’t have to redefine your entire project to add a DirectQuery node: As DirectQuery connectors and the Datastore are abstracted behind the IDatabase interface, the same cube definitions (measures, hierarchies…) can be used for all the nodes. A usual set-up to split “hot” and “cold” data is to use a date hierarchy:
  • the recent dates are put in-memory because they will receive a lot of queries and might have frequent real-time updates.
  • the older dates are put in an external data warehouse and accessed via DirectQuery because it accessed less frequently and receive rare updates. Part of this data can be pre-aggregated to provide an historical overview pretty quickly.
DirectQuery hybrid data distribution
These parts of the data will be stored in different places:
DirectQuery hybrid data distribution
With such a setup, the size of the in-memory data can stay reasonably small as most of the data stays in the external database. Moreover, queries will be fast enough for interactive analysis:
  • The majority of queries will be on recent dates and hit the in-memory nodes
  • Historical trends queries will hit the DirectQuery partial aggregate providers which are in-memory
  • When users start to drill down on historical data, the queries will be sent to the external database but at this point there should be a scope filtered enough (1 book on 1 date for instance) for the warehouse to answer quickly.