To create a temporary file, use uniq-file with a "temporary" clause. Temporary files are the same as any other files in the file-storage (and are organized in the same fashion), except that they are all under the subdirectory named "t":
/var/lib/gg/<app_name>/app/file/t
A temporary file is not automatically deleted - you can remove it with delete-file statement when not needed (or use a periodic shell script to remove old temporary files). The reason for this is that the nature of temporary files varies, and they may not necessarily span a given time frame (such as a lifetime of a request, or a lifetime of a process that serves any number of such requests), and they may be used across number of requests for a specific purpose. Thus, it is your responsibility to remove a temporary file when it's appropriate for your application to do so.
The reason for storing temporary files in a separate directory is to gain a separation of temporary files (which likely at some point can be freely deleted) from other files.
See uniq-file for an example of creating a temporary file.
