AWS Lambda appeared to be a nice method for task scheduling. In any case it is very cheap I only get billed for like 400ms per day. Other services like KMS came in quite handy as well - for instance to encrypt Bitstamp credentials in the configuration.
Right, 1.5% fee is ridiculous. Bitstamp charges 0.25%, that is ca. 2 cent for €5.
There are no guarantees that transaction will actually happen. But since the order goes to the last ask price, it is very probable that it will. I run this for a few days already, it always worked out so far. I also think that if the order is not executed for 24 our, Bitstamp will automatically cancel it (not quite sure, however).
