> Having types not line up at various boundaries (DB/API/reading from a file) is already a pain That's not really accurate - Postgres (for instance) types ARE

> Having types not line up at various boundaries (DB/API/reading from a file) is already a pain That's not really accurate - Postgres (for instance) types ARE mapped to Ruby types whenever you read something from the database, just like they are being mapped to Java types or any other language. I guess you mean you can have inadvertent type coercion where a Ruby string is saved into a PG numeric column or something? Anyway for super sensitive code (let's say payments/prices) you can work with DRY types or Sorbet or any other solution. As a rule it's quite rare that I actually see these problems. Can they occur? Sure. Do they happen so often I wish I was using C++? No. In fact I can't even say it happens more than once a year that I see this type of bug.