What should be the optimum values for Minimum cache lifetime and Expiration of cached pages i am working on a mobile app. Using drupal json views i am parsing the data and displaying on the device. It takes nearly 10 sec to load 10 records on the device. Initially i thought this might be due to slow internet, but that is not the issue. Later i came to know this is something related to cache. So can any one help me to minimize the loading time by suggesting minimum cache lifetime and expiration of cached pages .
The values of minimum cache lifetime and expiration of cached pages depends on how frequently the content on your site changes and for how long the external caches can show stale data from your site.

To get more info about these check https://drupal.stackexchange.com/a/83342/4876

However in your case I am not sure if these will matter. You should probably consider looking at Views Content Cache That might improve the performance in your case.