The 19-year-old reigning Asian champion beat Melian in a split decision of 2-1. (Agencies)
However, former cadet world champion Thokchom Nanao Singh (49kg) bowed out of the event after losing his prequarterfinal bout 0-3 to eighth seed Anthony Chacon Rivera of Puerto Rico.
Shiva will face Azerbaijan's Javid Chalabiyev in the quarterfinals and a victory will assure him of at least a bronze medal in the mega-event.
"It was a very tough bout and took a lot out of me but I somehow pulled through," Shiva told PTI as he caught his breath after the draining contest.
Shiva, a silver-medallist at the 2010 Youth Olympics, faced an opponent whose tactics were not too different from his own.
"I tried to play it cool in the opening round and it could have gone either way because we were quite similar in our style. It was a 50-50 thing. He clinched it and I increased my tempo in the next two rounds," Shiva said.
National coach Gurbax Singh Sandhu, while lauding Shiva, said it was one of the best bouts he witnessed.
"It was a very close bout and an excellent one at that. Both wanted to counter-punch, both of them had good footwork. But Shiva dominated the third round, which he won unanimously," said the long-serving coach.
However, it was the end of campaign for Nanao, who also endured a draining bout.
"Nanao also boxed very well but I guess the other guy managed to get ahead because of some uppercuts that he connected very clearly. I think Nanao was very good with his overall technique but then it happens," Sandhu said.
The Manipuri-lad, a former cadet world champion besides being an Asian Championships silver-medallist, lost 0-3 on points. Rivera was warned once in the third round but that could not help Nanao's cause.
The 19-year-old reigning Asian champion beat Melian in a split decision of 2-1.