Dealing with Big Lists
SharePoint stores your stuff in its databases. These are fast and well-designed SQL Servers.
But, if you’re not careful, you can still get slow-downs with big lists and libraries.
So what is big?
In SharePoint terms, 5000 items is big. You might have heard that this is a hard and fast limit. But that’s not true.
Firstly, this limit applies to views and queries, and not to the number of items in the list per se.
Secondly, you can reduce the impact, and the chance of hitting this limit, by adding SharePoint Column Indices to your lists and libraries on the Settings page.
SharePoint will take a guess and apply indices for you, based upon the views and queries your users make.
But, if you’re already over the 5000 item limit, and you create a new view, filtering by columns you’ve not filtered by before, you will hit problems.
SharePoint won’t let you add indices to lists with more than 5000 items in it.
Best practice is to work out what views and queries are likely to be made, and to put indices, in advance, on any columns you’ll use for filtering.