Put into bat, the hosts overcame an early blow to see big fifties from Iyer (83) and Duminy (78 not out) and put on board the highest total of this season so far.
New Zealand left-arm pacer Mitchell McClenaghan (2/38) struck in the very first over to send Mayank Agarwal back. The opener pulled a shortish delivery only to be holed out at short mid-wicket, where Ambati Rayudu took the catch.
Mumbai-born Iyer, who hit 7 fours and 5 sixes in his 56-ball stay, and Duminy, whose 50-ball knock was laced with 3 fours and 6 sixes, mixed with the right dose of caution and aggression, to take the attack to the opposition.
Iyer, who hit his second fifty of the season, was severe on medium-pacer Jasprit Bumrah (1-55), hitting the medium-pacer for a six and two fours to help DD get 16 runs off the 11th over.
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The duo continued its onslaught after the second time out post the 13th over as the 20-year-old Iyer smashed Harbhajan Singh (0-34) for two sixes and Duminy also brought up his second fifty of the season in the off-spinners final over that went for 18 runs.
Getting a little over-ambitious, Iyer was finally cleaned up by Lasith Malinga (1-23), in the 17th over, as the right-hander shuffled across to attempt a lap-scoop and the Yorker just sneaked in.
Guilty of giving away too many runs in his quota of overs, Bumrah did get a consolation wicket of Yuvraj Singh (2) in the final over of the innings. The final six deliveries fetched only 10 runs for the home team as Duminy carried his bat through.