Nandkumar is a former officer of the Indian Police Service. His police career involved stints in Jammu and Kashmir, in West Bengal, and in the Central Bureau of Investigation, covering anti-terrorism, local policing, and anti-corruption and economic crimes. He is a recipient of the Indian Police Medal for Distinguished Services.
Nandkumar took early retirement in 2008 to specialise in cyber security, and technology and risk management. He served as chief executive officer of ReBIT, a subsidiary of the Reserve Bank of India (RBI), responsible for technology management and cyber security for RBI's systems, during 2016-21. In his private sector phase, he has worked in senior positions in ICICI Bank, Citibank and EY, apart from being the CEO of Data Security Council of India.
Nandkumar holds a master's degree in environmental engineering. He is a Fellow of Salzburg Global Seminar.