This week, I faced the problem of having to delete 1.7 million features in a feature service in ArcGIS Online. Normally, I would make a remote connection to the server, access the geodatabase and delete the features with a few mouseclicks. However, ArcGIS Online has no such feature. So I had to resort to the REST interface to the feature service: deleteFeatures. The API reference can be found here. Pretty straightforward, I would say.
But after waiting for a few (or rather: a lot of) seconds, I got a server timeout. It seems that 1.7 million features is rather too much to manipulate through the REST interface. I had to do this in batches. When talking about batches, Python jumps to mind. So I constructed a very small Python script, that also can be used to demonstrate the way you can manipulate ArcGIS Online feature services through the REST interface.