The Saints racked up eight scores and a half century of points as they kept up their end of the bargain in the race for Anglo-Welsh Cup semi-final qualification.
The captain Ben Foden started the scoring with his 50th try in black, green and gold, doubling up later in the first half and followed over by five teammates including James Fish, at the other end of the scale with a first pair of senior Saints scores.
They would trail twice inside the opening quarter, however, Scarlets keeping the ball well around halfway and Billy McBride kicking the visitors into an early lead.
The Gardens didn’t have to wait long for a response and having seen one maul disrupted illegally by their visitors, the Saints played off the back of another, eventually getting it wide where Foden produced a fine finish under pressure.
It was an effort soon matched by Tom Williams at the other end, the wing ghosting past defenders and stretching to re-establish a Scarlets lead that would again last just a few minutes. With Saints putting pace on the ball at every opportunity, Gibson opened his stride to glide through and level things, Myler edging the hosts ahead with a well struck conversion.
Back ahead, things were by no means comfortable for the Saints, Joneses Dion and Rhodri both finding gaps through the home line but running out of support when black shirts scrambled to the scene. Those scares though seemed to act as something of a wake up call and back in enemy territory Foden was again the finisher, this time brilliantly gathering a pin point Stephen Myler cross-kick on the right.
A thoroughly entertaining first half was rounded off with the bonus point score, too, Mikey Haywood driven over from a five-metre lineout and the scoring would resume soon after the restart, Harry Mallinder breaking the line and diving beside the posts for a Saints fifth.
Saints weren't taking their foot off the gas and a flowing backs move saw Ken Pisi come from round the corner to arc through and over before the forwards rejoined the party, mauling Fish over from close range following sustained pressure inside the Scarlets' 22.
Having endured a damaging half an hour, the young Scarlets reacted well and again began to exert some pressure as the heavens opened in Northampton. But while they would keep their hosts pegged in for the best part of 20 minutes, a consolation score was not forthcoming.
Instead, it was left to the Saints to round off the scoring, Fish riding another brutal maul over to take the hosts to the magic 50-point mark and keep their qualification hopes alive - a favour now needed from Tigers on Sunday afternoon.
4mins SCARLETS Pen McBride 0-3
7mins SAINTS Try Foden 5-3
12mins SCARLETS Try Williams Con McBride 5-10
17mins SAINTS Try Gibson Con Myler 12-10
27mins SAINTS Try Foden Con Myler 19-10
40mins SAINTS Try Haywood 24-10
HALF-TIME SAINTS 24-10 SCARLETS
44mins SAINTS Try Mallinder Con Myler 31-10
50mins SAINTS Try K Pisi Con Myler 38-10
55mins SAINTS Try Fish 43-10
80mins SAINTS Try Fish Con Myler 50-10
SAINTS 50-10 SCARLETS
Tuala; K Pisi, Tuitavake, Mallinder, Foden (capt); Myler, Groom; E Waller, Haywood, Brookes, Paterson, Day, Gibson, Ludlam, Dickinson
Fish, A Waller, Hill, Ribbans, Craig, Dickson, Hutchinson, Estelles
D Jones; Williams, Smith, R Jones, Griffiths; McBride, Lloyd; Robinson, Hughes, Sebastian, Helps, Bernardo, Phillips, S Evans, Allen (capt)
Fawcett, Myhill, Watkins, Dy, Condy, Cole, Maynard, A Evans