John is a Senior Computer Scientist at Lawrence Berkeley National Laboratory. He works on data management, data analysis, and scientific computing. His algorithmic research work includes feature extraction, indexing techniques, tensor data processing, and scientific computing. He has authored more than 200 technical publications, 19 of which have more than 100 citations each.

He has packaged some of his algorithms into efficient software packages. Among them, the FastBit indexing software has won an R&D 100 Award, and is used by many organizations. For example, a German bioinformatics company uses FastBit to accelerate their molecular docking software by hundreds of times, and a US internet company uses it daily to sift through terabytes of advertisement related data. The FastBit software was also counted among 40 major works funded by the US Department of Energy (DOE), Office of Science, showcased at its 40th Anniversary celebration in 2018.