After succumbing to a thrashing against Edinburgh in their previous match, Scarlets narrowly beat Cheetahs in Pro14.
The standout team in Pro14 could only manage a 3-0 win against winless Zebre as Leinster struggled on Saturday.
Scarlets made it three from three in Pro14 on Sunday as Glasgow Warriors earned a first win of the season.
Ulster suffered a hammering in Bloemfontein, where wing Anthony Volmink scored three of nine tries for the Cheetahs.
Dave Kearney's hat-trick helped Leinster begin the defence of their Pro14 title with a win over Benetton Treviso.
The fixtures for the 2019-20 Champions Cup and Challenge Cup have been revealed, with Saracens starting their title defence at Racing 92.
Munster, Racing 92 and the Ospreys will take on holders Saracens in the pool stage of the 2019-20 European Champions Cup.
Edinburgh's Pro14 play-off hopes hang by a thread after a damaging home defeat to Ulster, who extended their own domestic season.
Iliesa Ratuva Tavuyara touched down and Tommaso Allan converted with the last play of the game as Benetton Treviso held Leinster in Dublin.
Cardiff Blues used Wales Grand Slam heroes Gareth Anscombe and Josh Navidi from the start in their demolition of the Scarlets.
Wales international Leigh Halfpenny featured in the Scarlets' 10-6 win over Munster, while Glasgow Warriors went top of Conference A.
Luca Sperandio and Niccolo Cannone scored two tries apiece as Benetton Treviso stretched their unbeaten run to eight games.
Zebre put on a spirited showing but ultimately fell short against Pro14 heavyweights Leinster.
Benetton Treviso's winning run was ended at five matches as Ulster earned a dramatic draw in the Pro14.
Northampton scored 17 tries in a record victory as they beat Timisoara Saracens 111-3 to reach the European Challenge Cup quarter-finals.
Ryan Mills' last-gasp drop goal put Worcester Warriors into the last eight of the Challenge Cup for the first time in a decade.