Many databases or database clients have an "upsert" operation which is exactly this. Create or update this entity. If the DB supports it you can save an explicit lookup giving minor performance and code cleanliness improvements in application but might shift that performance cost to the DB (had to rollback a prod change not too long ago because someone switched to a PG upsert and it caused average CPU to rise, haven't gotten a chance to investigate why yet, something about indexes probably).

Anyway, I tend to start with just explicit create and update methods and add an "upsert" abstraction if I find myself sprinkling lots of checks around making code messy. So I would go for "createOrUpdateFoo" in that case.