I hope that you are using Postgres partitions for this. Depending on your data size, you could ease sorting by date for the 'last month' by day, week or month. This will have an added benefit of requiring less ram for most of your selects and otherwise increasing the speed of your queries.
For us, I/O isn't as big a cost factor, since our data processing mostly resides in ephemeral storage where I/O charges don't apply. (Our permanent data backups live in S3.)
Very true. This is basic stuff, and we simply overlooked it. In the future, we might even need to add increased redundancy to our data, which we need to be aware of.
I hope that you are using Postgres partitions for this. Depending on your data size, you could ease sorting by date for the 'last month' by day, week or month. This will have an added benefit of requiring less ram for most of your selects and otherwise increasing the speed of your queries.