a, b := results[i], results[j]
		if a.oi.ModTime.Equal(b.oi.ModTime) {
			// On tiebreak, select the lowest pool index.
			return a.zIdx < b.zIdx
		}
		return a.oi.ModTime.After(b.oi.ModTime)
	})

	for _, res := range results {
		err := res.err
		if err == nil {
			return res.oi, res.zIdx, nil
		}
		if !isErrObjectNotFound(err) && !isErrVersionNotFound(err) {
			// some errors such as MethodNotAllowed for delete marker