In 2009 he was visiting assistant professor in the CS Dept., Stanford University. Before that, he was assistant professor in the CS Dept., National University of Singapore (NUS). In the past he was involved in the designing and testing of VLSI chips and worked in several companies on database designing, e-commerce projects and web applications. He has served as associate editor for the IEEE Transactions on Knowledge and Data Engineering (TKDE) from 2013 to 2015, and on the editorial board of the VLDB Journal from 2013 to 2017. Currently he is on the editorial board of the Data Science and Engineering Journal. He received his Diploma from the Computer Engineering and Informatics Dept., Univ. of Patras, Greece in 1998 and his PhD from the Computer Science Dept., Hong Kong Univ. of Science and Technology (HKUST) in 2002. His research interests include Big Data, Cloud Computing, Parallel and Distributed Systems, Large Graphs and Long Sequences.