We're trying to add some kind of persistence in our app. The app generates about 250 entries per second. Each of these entries belong to one of 2M files. For each file, we want to keep the last 10 entries, so we can look them up later.

The way our client application works :

• it gets a stream of all the data
• it fetches the right file (GET)
• it adds the new content
• it saves the file back (PUT)

We're looking for an efficient way to store this data that can scale horizontally as the amount of data we're getting is doubling every few weeks.

We initially looked at S3. It works fine, but becomes very expensive very fast (>$1000 monthly just in PUT operations!)

We then gave a shot at Riak. But it seems we can't get more than 60 write/sec on each node, which is very very slow.

Any other solution out there?