A catalogSnapshot record is one immutable snapshot of the Racket package catalog. Record keys are TIDs, so multiple snapshots in a day are allowed. publishedAt and createdAt are separate: publishedAt is when the upstream snapshot finished building, so consumers see when it really appeared rather than when we happened to poll for it. Both are UTC with a Z suffix. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>