The KV store had etag support for conditional writes. Etags are only useful to make sure the data didn't change underneath between your read and your write.
Storing the checkpoints along with the mutation was for idempotency. If the checkpoint was in the document, that meant the mutation had succeeded and a retry should be no-op
Storing the checkpoints along with the mutation was for idempotency. If the checkpoint was in the document, that meant the mutation had succeeded and a retry should be no-op