Adding a single graph for a $2000/mo DB, only performing read only transactions at 30% of its connection limit doesn't sound like putting the DB through its paces, and not real world.
The bottom of the bar chart says: Database performance was measured using pg bench with 150 concurrent clients performing read-only transactions.
pgbench[1] is a performance benchmarking tool that is part of PostgreSQL itself. It ships alongside the rest of the PostgreSQL binaries and is open source just like the rest of PostgreSQL.
I think this line from the article is interesting:
> In addition to Heroku Postgres DbX we are launching new database plans with double the memory and speed improvements of up to 3x at the same price as our current plan lineup. These plans feature an upgraded and re-engineered infrastructure to drastically improve their memory and speed.
I wonder if the bulk of the price/performance gains are from switching to newer instance types on AWS and/or switching the underlying storage from magnetic disks to the new SSD EBS volumes[2].
[1]: http://www.postgresql.org/docs/devel/static/pgbench.html
[2]: http://aws.amazon.com/about-aws/whats-new/2014/06/16/introdu...