They have teams maintaining/debugging/operating their use/consumption of dynamodb; they don't have teams maintaining/debugging/operating/securing dynamodb itself.

With LedgerDB, they now have to do both.

Optimizing to address high percentile issues (latency/error/correctness) on someone else’s code follows a bimodal pattern: it’s easy until it is impossible. Doing it on your own code is progressively more difficult and the complexity may cause you to give up, but you normally don’t hit the same wall.