I'm occasionally having issues when trying to query user json formatted inventories. I'm getting 429 errors which means too many requests but what's the actual limit?
What I've done to make less requests is cache the bot inventory for 3-4 minutes and cache the users inventory for 1 minute. Even then I'm greeted with 429 sometimes.
I did this in PHP but as far as I know the tradeoffer-manager uses the same endpoint for inventory requests.