McDonald had to wait for the final race to bring up his historic "ton" as Kordia unleashed a powerful surge to win the Hyland EOFY Sale Handicap (1200m) after earlier scoring aboard Rothenburg and Roheryn to take his tally of Sydney winners to 100.5 for the 2019-20 season.
McDonald, who rode 104 winners to claim the Sydney jockeys' premiership last year, is the first to ride at least 100 metropolitan winners in successive seasons since Darren Beadman in 2007 and was delighted to achieve his goal.
"I was thrilled and extremely happy as it was a goal I had set out to achieve," McDonald said.
"I had great support through a wide base of trainers and owners and we couldn't have done it without that support.
"It's a hard environment that we compete in and so to do it twice is such a really good thing to achieve.
"We've fought away at it and hopefully I can get a few more before the end of the season."
McDonald gave plenty of praise to the team around him including his agent Mark Guest.
"Monday is quite stressful for Guesty as he is working through rides up to two weeks in advance," he said.
"We sit down and try and work through them and pick the best ones although there is always a loyalty to the bigger supporters.
"He does a great job communicating with everyone and we work really well together.
"I also got to speak with my mum back in New Zealand (after the win on Kordia) which was really nice.
"She is devastated she hasn't been able to come over as she was there for my 100th last year but she's very happy and it is always good to talk to family back home."
McDonald has his sights set on retaining his Sydney jockeys' premiership despite the three-week suspension that runs from July 5 to July 26.
He currently holds what seems an unassailable 20.5-win lead over nearest rival Nash Rawiller (80 wins) but won't be resting on his laurels with whatever time he has left in his season.
"It will be my main focus as I would love to achieve that goal as well," he said."It would cap off a wonderful year."