Configure cache settings for a web application in SharePoint Server 2013

when need to setup blob cache  ?  one of the reasons is you want keep the file (document , video) at web front end , so no need very access need to extract from SQL server.

https://technet.microsoft.com/en-us/library/cc770229.aspx

To configure BLOB cache settings

1. Verify that you have the following administrative credentials: You must be a member of the Administrators group on the local computer to configure the BLOB cache settings.
2. Click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
3. In Internet Information Services (IIS) Manager, in the Connections pane, click the plus sign (+) next to the server name that contains the web application, and then click the plus sign next to Sites to view the web application or applications that have been created.
4. Right-click the name of the web application for which you want to configure the disk-based cache, and then click Explore. Windows Explorer opens, with the directories for the selected web application listed.
5. Right-click web.config, and then click Open.
6. If the Windows dialog box appears, select Select a program from a list of installed programs, and then click OK.
7. In the Open With dialog box, click Notepad, and then click OK.
8. In the web.config Notepad file, find the following line: 
9. In this line, change the location attribute to specify a directory that has enough space to accommodate the cache size.

   Note:
   We strongly recommend that you specify a directory that is not on the same drive as where either the server operating system swap files or server log files are stored.

10. To add or remove file types from the list of file types to be cached, for the path attribute, modify the regular expression to include or remove the appropriate file extension. If you add file extensions, make sure to separate each file type with a pipe (|), as shown in this line of code.
11. To change the size of the cache, type a new number for maxSize. The size is expressed in gigabytes (GB), and 10 GB is the default.

    Important:
    It is recommended that you not set the cache size smaller than 10 GB. When you set the cache size, make sure to specify a number large enough to provide a buffer at least 20 percent bigger than the estimated size of the content that will be stored in the cache.

12. To enable the BLOB cache, change the enabled attribute, from "false" to "true".
13. Save the Notepad file, and then close it.