I think there's a clear critique of Cassandra in there, in that it shouldn't even be possible to configure nodes to serve data they don't have.
Monzo... It's very hard to say. I think based on the contents of the blog post they acted reasonably and competently (yeah, the test rollout was a badly designed test, but that's easy to say post hoc). The only fair basis for critiquing Monzo would be if they had notably more averages than is 'typical', and we don't have the data or conceptual framework required to do that. As a customer, I can't think of risks that Monzo exposes you to that aren't also present with other banks. I bank with them ¯\ _(ツ)_/¯
Monzo... It's very hard to say. I think based on the contents of the blog post they acted reasonably and competently (yeah, the test rollout was a badly designed test, but that's easy to say post hoc). The only fair basis for critiquing Monzo would be if they had notably more averages than is 'typical', and we don't have the data or conceptual framework required to do that. As a customer, I can't think of risks that Monzo exposes you to that aren't also present with other banks. I bank with them ¯\ _(ツ)_/¯