AWS also has Kinesis, which is deliberately intended to be a sort of event drain. Under the hood it uses S3 and they publish an API and an agent that handles all the retry / checkpoint logic for you.
If you want to keep a lot of data for ad-hoc queries but only use a subset for regular queries then consider setting up separate dense compute and dense storage Redshift clusters as appropriate. As far as pricing goes there's a hell of a discount for going reserved once you've got things set up the way you want them.
Once you've got that running and the immediate fires are out you may want to look at Spark to pre-compute some of the reports (you can still push the computed data into Redshift tables to save changing the reporting too much), although I don't think spark as a service isn't really there in AWS right now, and running up an EMR cluster is seriously going to cost you.
Bigtable provides similar capabilities to Redshift in the google ecosystem, and looks okay although I wasn't blown away by it.