"When all other students will quietly listen to what I would teach, he will ask a lot of questions - 'why does it have to be like this, why can't we do it like this'," said Harishchandra Hebbar, who taught digital electronics to Nadella at Manipal University.
"Sometimes it felt like he was just testing my patience," said Hebbar, laughing.
That questioning nature has served Nadella well in his 22-year career at Microsoft, the world's largest software company. Last year he was promoted to run the company's fast-expanding cloud, or Internet-based, computing initiatives.
His elevation to the top spot at Microsoft would end a five-month search for a tech-savvy heavy-hitter to lead the company co-founded by Bill Gates. A source familiar with the matter told Reuters on Thursday that Nadella's appointment was likely, although the board had not yet met to finalise it.
Nadella grew up in Hyderabad, a technology hub that is home to the biggest Microsoft research and development centre outside of the United States.
His father was a member of the elite Indian Administrative Service and a member of the Planning Commission during 2004-2009 under Prime Minister Manmohan Singh. His father, B. N. Yugandhar, who still lives in Hyderabad, declined to speak with Reuters when reached by phone.
Born in 1967, Nadella attended the prestigious Hyderabad Public School, where he met his future wife. Nadella studied electronics and communication engineering, at Manipal University, where people who knew him at the time described him as friendly, modest and well-spoken.
Manipal is a mid-ranking private institution, and does not have the cachet of the elite Indian Institute of Technology (IIT) and Indian Institute of Management (IIM) where many of India's global power players were educated.
If he gets the top job at Microsoft, Nadella would join the growing list of Indian-born executives to head a major global corporation. They already include PepsiCo Inc CEO Indra Nooyi and Deutsche Bank co-CEO Executive Anshu Jain.
After graduating in 1988, Nadella, like many ambitious Indians, moved to the United States to study, earning a master's degree in computer science from the University of Wisconsin-Milwaukee.
Ganesh Prasad, a classmate of Nadella at Manipal who remains in touch with him, recalled a conversation in 1991 when Nadella was working at Sun Microsystems.
"We were having a conversation and talking about Sun as the future of hardware ... and he was like: 'you know where I need to go I need to be in software and I need to be in marketing and I need to be in Microsoft'," Prasad recalled by phone from Bangalore, where he now lives.
Prasad, who worked for 20 years in the United States with Intel Inc, said Nadella started with a base in technology and then became interested in how to market it - a skill set that will be called upon in his new role.
By comparison, Microsoft's previous CEO, Steve Ballmer, was regarded more as a salesman and cheerleader than a technology visionary.
"While he comes from a very strong technology background, his outlook over the years has changed to: 'so, what, what am I going to do with this thing How do I position it How do I make sense of it all'," said Prasad.