In this section, we will review when system and custom indexes maintained by the Force.com platform are used to make queries more performant and, once larger query results are returned, the ways in which they can be most effectively consumed by your Apex logic.
As with other databases, Force.com maintains database indexes as record data is manipulated to ensure that, when data is queried, such indexes can be used to improve query performance. Due to the design of the Force.com multitenant platform, it has its own database index implementation (instead of using the underlying Oracle database indexes) that considers the needs of each tenant. By default, it maintains standard indexes for the following fields:
Any Master Detail fields
Any Lookup fields
Any fields marked as Unique
Any fields marked as External Id
Once your application...