Two goals in the space of four minutes at the end of the first half saw Derry City move into prime position for a top three finish and Europa League football next season.
And for Cork City, this will be a performance to forget, new boss, Neale Fenn suffering his fifth defeat during the first six games of his tenure.
Indeed, it was clear from the outset when opting for a flooded midfield, that Cork’s tactics had been based on containment given that Premier Division status had yet to be secured.
Happy to defend in numbers and hit on the break, Derry were happy to carry the ball forward, always aware that a victory would leave them well placed for a return to European football next season.
And it was the home side who created the first clear-cut scoring opportunity when a Ciaron Harkin cross from the left saw David Parkhouse head the ball wide in the 12th minute when racing forward.
Five minutes later the lively Derry hitman forced Tadhg Ryan into a top drawer save, the Cork keeper diving a full stretch to superbly touch Parkhouse’s rising shot from 20 yards over his crossbar.
In the 25th minute Parkhouse again threatened the Cork defence when he outfoxed Shane Griffin before flashing another shot high over the crossbar.
The 22-years-old Limerick native impressed again as he rose above his defence to secure possession when called upon as Derry flattered to deceive in the frontline, a situation which had prevailed on Foyleside over recent weeks.
In fact the Cork bench will have breathed a sigh of relief in the 37th minute when former Derry player, Eoghan Stokes, produced a late and over-robust challenge on Harkin close to the end of the Derry penalty area.
And given that Stokes had received a yellow card in the 17th minute, the decision of referee Derek Tomney not to produce a red card did not go down well with the home attendance of 2,000.
However, as the game approached half-time, the home support celebrated when Derry moved firmly into the driving seat.
The Cork defence failed to clear a long throw-in which reached the danger area and when the ball was headed down by a visiting defender, Derry centre-back, Eoghan Toal, swept it home from close range.
And it got even worse for the ‘Leesiders’ as the game entered additional time at the end of the first half.
Central midfielder, Conor McCormack, played a loose pass just outside his penalty area and when Harkin combined with Junior Ogedi-Uzokwe the Colchester United loanee calmly curled the ball beyond the reach of the advancing Ryan and Cork were in serious trouble.
Karl Sheppard flashed a decent shot over the Derry crossbar in the 84th minute but it was always a case of too little, too late.
Neale Fenn introduced a double substitution within seven minutes of restart with McCormack and Stokes called ashore, replaced by Garry Buckley and Joel Coustrain and the visitors began to threaten.
That said Cork then lost captain, Conor McCarthy in the 60th minute due to a head wound following a collision with Junior.
Buckley began to force Derry keeper, Peter Cherrie, into action for the first time, the Derry defence seeing much more of the ball.
While Cork certainly upped the ante after the break, the home side were happy to sit back and hit on the break and Ryan did well to punch a powerful shot from Derry sub, Darren McCready, clear of his goal in 70th minute.
However, four minutes later this game was ended as a contest, another disaster for Cork who conceded an own goal and Derry three goals to the good.
A header by Junior was parried by Ryan but the rebound cannoned off the body of the unsuspecting full-back, Colm Horgan, from close range, the ball deflected into the net.
A decent shot by Karl Sheppard which screamed over the crossbar and a close range header by sub, Alan Bennett, which was saved by Cherrie, threatened to reduce the deficit late on, but those effort were always considered too little, too late.
Derry had the final say when Junior made it 4-0 deep into added time.
DERRY CITY: Cherrie; Gillespie (Boyce, 85), Toal, Gilchrist, Coll; Harkin, Sloggett, Malone (McCauley, 58), Ogedi-Uzokwe; McNamee (McCrudden, 78); Parkhouse.
CORK CITY: Ryan; Horgan, O’Brien, McCarthy (Bennett, 61) Griffin; Sheppard, McCormack (Buckley, 53) Morrissey, Byrne, O’Connor; Stokes (Coustrain, 53).