Keith won heat five by clocking 23.33s. However, he only finished 22nd overall, 0.92 second short of qualifying for the top-16 semi-finals.
"I equalled my personal best today... satisfied with the time as I have not swum this fast since the Sea Games last year. I could have done better or worse, so I am not complaining," said Keith.
"However, I wasn't satisfied with my 100m freestyle performance on Sunday. I need to work on my speed to improve my time."
|Gold Coast 2018 Commonwealth Games - Men's 50m Freestyle - Heats - Optus Aquatic Centre - Gold Coast, Australia - April 9, 2018. Keith Lim Kit Sern (2nd R) of Malaysia prepares for the event alongside fellow competitors. — REUTERS pic|
Compatriot Caroline Chan clocked 30.10s, 0.50 seconds off her national record set at the 2016 Asian Championships in Japan, in the women's 50m backstroke.
She finished 18th overall.
"I had hoped to break my national record here. I need to learn how to control my nerves and swim better," said Caroline.
Both Keith and Caroline will compete in next month's Malaysian Open in Kuala Lumpur which is a qualifier for the Indonesia Asian Games later this year.
The swimmers ended their campaigns commendably though they did not win medals.
Tern Jian Han and Welson Sim were the stars by reaching the finals of the 50m backstroke and 400m freestyle events.