Thanks for reposting your question here.

Replicating my answers from Slack:

1. We’re very conservative about adding new columns and favor using meta for extra information like this.
2. If you want something consistent right away, then stash a timestamp in meta when you insert the job and use that for your calculation.

The issue with scheduled_at is that snoozing or retrying overwrites it. So, thinking about this a little more after our earlier, I realized that Oban can preserve the original timestamp itself (at least Pro can). This commit just landed in the v1.4 branch:

Record orig scheduling time on snooze and retry

Snoozing and rescheduling a job on error overwrites the scheduled_at
timestamp, which makes it impossible to determine how long a job was
truly waited before execution.

Now snoozing or erroring will inject the original scheduled_at
timestamp as unix seconds into the job’s meta as orig_scheduled_at.

You’ll be able to get a reliable scheduled_at for the age calculation:

case job.meta do
  %{"orig_scheduled_at" => unix_at} -> DateTime.from_unix(unix_at)
  _ -> job.scheduled_at
end