[rockwotj]

I honestly don't think I've seen people reason about read committed well, especially as an application grows it becomes very difficult to understand all the cases in which locks are grabbed/data is accessed. (I feel that way about multi-threaded code and locks too, but that's for another time).

So I really only see serializable to be the only sane isolation model (for r/w transactions), and snapshot isolation is a good model for readonly transactions (basically you get a frozen in time snapshot of the database to work with). This also happens to be the only modes in which Spanner gives you: https://cloud.google.com/spanner/docs/transactions