Scala 3 in anger: what changed for our data team

We migrated our core data libraries to Scala 3 a year ago. This is the honest retrospective — what helped, what cost us, and what we still avoid.

Earned their keep

• Given/using clauses made our implicit-heavy code finally readable to newcomers.
• Enums replaced a pile of sealed-trait boilerplate.
• The new error messages are dramatically better, which matters more than any feature.

The migration itself cost about three engineer-weeks of cleanup. For a codebase this central, that paid for itself within the quarter.