Question: I'm using gae for a project and I have a cron script to keep it alive so that the handful of users I have so far wont have to wait +5 sec on their first query.

Does anyone know if Google will enforce some limit on my app if the logs reflect that there are significantly more hits from the cron script than actuall users?

Thanks

Answer: 
I don't know if Google would enforce a limit or not. 

Instead of using a cron job, you can [set the min idle instances to 1(or more)](https://developers.google.com/appengine/docs/adminconsole/performancesettings#Setting_the_Number_of_Idle_Instances) if you're worried about response time. 
Enable billing to do this.
so far google has no such criteria but better option is enable billing with automatic scaling 
it really helped me to pace my site's speed.

if you are really worried on pace increase min idle instance and decrease pending latencies you can find them on your dashboard if your app has billing enabled.