} elseif ( $dataCombinedLag > self::MAX_READ_LAG ) {
            $pregenCombinedLag = ( $walltime !== null ) ? ( $dataCombinedLag - $walltime ) : 0;
            // Case D: medium snapshot lag with medium replication lag
            if ( ( $pregenCombinedLag + self::GENERATION_HIGH_SEC ) > self::MAX_READ_LAG ) {
                // Case D1: generation started when read lag was too high