I'm happy to spin up 10 app servers rather than make the single database faster, but I'm not sure these apps would be offloading much from the database just by doing "joins" in-memory.

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Microsoft is building its SQL Server database so it will have an in-memory database to compete with the likes of SAP's Hana and Oracle's Exadata. Codenamed “Hekaton” the new in-memory database ...