Former British Grand Prix winner Jeremy McWilliams was among the hundreds of mourners who gathered at Ballylinney Presbyterian Church to pay their last respects to Mr Keys.
Bikers from across the UK attend in their own team clothing.
Stewards and race officials provided a racer's guard of honour as Mr Keys the coffin left the church.
Mr Keys only took up competitive racing in 2013.
But by 2015 he had finished the season as runner-up in both the Ulster and Irish Supersport Cup Championships.
He then decided to tackle the roads and made his debut during the Cookstown 100 just over a year ago, where he dramatically came off his Suzuki at Braeside corner in the Senior Support race.
He won the Enniskillen Senior Support race in 2018 and decided to plan another road campaign in 2019.
After finishing second in the Senior Support races at Cookstown and Tandragee, Mr Keys won his first race of this season again at Enniskillen and followed that up by winning at Skerries last weekend on his distinctive Suzuki.
These results had put him into contention for the 2019 Irish road race Senior Support championship, of which Walderstown was a counting round.
He was killed after crashing in the Senior Support race and the event was subsequently abandoned.
Mr Keys received on-track medical attention before being transferred by helicopter to the Mater Hospital in Dublin, but unfortunately succumbed to the seriousness of his injuries.
The Gardai is investigating the crash.
To donate to help the family visit: www.gofundme.com/f/darren-keys-memorial-fund-94