I have also found out that /api/items is loading up but when I hit to any commerce category it exceeds time and throws timeout exception

https://status.netsuite.com/#dtc=se4# Have a look if this is your server.

I would double check if your index is rebuilding or a category is quite new. Also if you running on CDN it might take a while to fully propergate.

@karlenigma I have disabled CDN and things are working fine

Thought as much. The CDN is a pain!

@karlenigma now even after disabling the CDN we are not able to fetch data from items api

Seems a bit odd. I would check in the dev console to see if you can retrieve in there first. Also check the network tab to make sure item API is running.

So I ave checked that and observed that normal search works fine, but when we fetch data from commerce categories there seems to be a problem

I would make sure every thing is enabled and setup correctly.

this is a production issue and we haven't made any changes

Strange