I am a Senior Researcher at Microsoft Gray Systems Lab since May 2025.

I recently got my Ph.D. from University of Wisconsin-Madison advised by Paraschos Koutris. I work on techniques to optimize (or show optimality for) relational queries. Paris' ICDT'25 keynote is a great survey of many of these ideas.

In 2020, I received my B.S. in Math from National University of Singapore. There, I was advised by Prof. Jonathan Scarlett on neural architectural search.

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News

• December 2025: FlowLog has been accepted to VLDB 2026. Visit the website if you are interested in working with us!

• November 2025: I gave a talk at NWDS on our recent research efforts on "Modernizing the Yannakakis Algorithm".

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Publications (* denotes alphabetical authorship)

• FlowLog: Efficient and Extensible Datalog via Incrementality website
  Hangdong Zhao, Zhenghong Yu, Srinag Rao, Simon Frisk, Zhiwei Fan, Paraschos Koutris
  VLDB'26

• I Can't Believe It's Not Yannakakis: Pragmatic Bitmap Filters in Microsoft SQL Server (coming soon)
  Hangdong Zhao, Yuanyuan Tian, Rana Alotaibi, Bailu Ding, Nicolas Bruno, Jesús Camacho-Rodríguez, Vassilis Papadimos, Ernesto Cervantes Juárez, Cesar Galindo-Legaria, Carlo Curino
  CIDR'26

• *Circuit Bounds for Conjunctive Queries with Self-joins
  Austen Fan, Paraschos Koutris, Hangdong Zhao
  PODS'25

• Output-sensitive Conjunctive Query Evaluation
  Shaleen Deep, Hangdong Zhao, Austen Fan, Paraschos Koutris
  PODS'25
  Best Paper Award (invited to J. ACM)
  SIGMOD 2026 Research Highlight Award

• Evaluating Datalog over Semirings: A Grounding-based Approach Datalog 2.0'24
  Hangdong Zhao, Shaleen Deep, Paraschos Koutris, Sudeepa Roy, Val Tannen
  PODS'24

• *Tight Bounds of Circuits for Sum-Product Queries slides
  Austen Fan, Paraschos Koutris, Hangdong Zhao
  PODS'24
  Distinguished Paper Award (invited to J. ACM)

• Predicate Transfer: Efficient Pre-Filtering on Multi-Join Queries
  Yifei Yang, Hangdong Zhao, Xiangyao Yu, Paraschos Koutris
  CIDR'24

• Conjunctive Queries with Negation and Aggregation: A Linear Time Characterization slides demo TODS'25
  Hangdong Zhao, Austen Fan, Xiating Ouyang, Paraschos Koutris
  PODS'24
  Distinguished Paper Award (invited to TODS)

• *The Fine-Grained Complexity of Boolean Conjunctive Queries and Sum-Product Problems slides poster
  Austen Fan, Paraschos Koutris, Hangdong Zhao
  ICALP'23

• Space-Time Tradeoffs for Conjunctive Queries with Access Patterns slides TODS'25
  Hangdong Zhao, Shaleen Deep, Paraschos Koutris
  PODS'23
  Distinguished Paper Award (invited to TODS)

• On Architecture Selection for Linear Inverse Problems with Untrained Neural Networks
  Yang Sun, Hangdong Zhao, Jonathan Scarlett
  Entropy, 23(11), 1481

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Teaching Experience (TA)

• CS 577 Intro to Algorithms: Spring 2022 (Prof. Jin-yi Cai), Fall 2021 (Prof. Eric Bach)

• CS 544 Intro to Big Data Systems: Fall 2023 (Prof. Tyler R. Caraza-Harter)