this is pretty weird for me to hear, as a developer on a project with 3000+ monthly average users where DynamoDB is my only database and the costs are in the hundreds per month.
I'm sure that any database can be "too expensive" if your access patterns are out-of-this-world intense, but it's very difficult to compare apples to apples when we have no idea how beefy the PostreSQL instance to support your cache would have been.
pretty intense, yes. for each user who uses it, they take several hundreds of actions per day that each require a database write. we could optimize those but it's not worth it.
Like you said, hard to compare apples-apples without more info but couple 1000 users with 100s of writes/user/day sounds like it would handle fine on a $1/month vps (we have far higher workloads running few $1/mo, if I understand you correctly).
Not saying that you should spend time on that; it's probably insignificant on the p&l, however, other people should know there are alternatives still and aws is not always, automatically, the right choice (in my mind, it almost never is actually).
