RDS is such a depressing database option. It does not matter how much money you throw at it, its performance will always be limited by the awful disk IOPS. Luckily these days you can easily run PG on EC2 (or simply use CRDB).
Weird for Heroku to ignore this huge efficiency opportunity.
io2 is generally better than io1, one advantage is that you can scale storage size and IOPS independently. That being said, RDS with io2 is still worse than an ec2 instance with nvme (a lot worse)
Weird for Heroku to ignore this huge efficiency opportunity.