Jung-Sang Ahn

안정상 (in Korean)
Software Engineer at eBay.

LinkedIn
Github
YouTube [Music] [Trackday]
SoundCloud

Interests

• Distributed systems
  • Replication/consensus protocol (Paxos, Raft)
  • On-disk indexing (B+tree, LSM-tree)
  • Secondary indexing
  • Query processing
  • Transaction and conflict resolution
  • Caching
• Music
  • Electric/acoustic guitar
  • Fingerstyle guitar
  • Songwriting
  • Recording, mixing, and mastering
• Sports
  • Snowboarding
  • Trackday
  • Road bike
  • Go-kart

Employment and Education

• Principal MTS (Director), eBay, 2017-present.
• Senior Software Engineer, Couchbase, 2015-2017.
• Ph.D. in Computer Science, CASYS lab, KAIST, 2010-2015.
• M.S. in Computer Science, CASYS lab, KAIST, 2008-2010.
• B.S. in Computer Science, KAIST, 2004-2008.
  • Presidential scholarship, the Korean government.
• Daejeon Science High School, 2002-2004.
  • Early graduation, 2 years.

eBay

• Development of eBay's own database fleet
• Geo-distributed, highly available databases serving trillions of requests/day.
• Multi-master key-value store, global secondary index store, document store, graph store.
• Own replication engine based on Raft and variants.
• Original author of NuRaft
• Own storage engine based on LSM-tree, B+tree, and variants.
• Original author of Jungle
• Own query engine that processes SQL-like requests through low-level key-value operations.


• Core functionalities
• Distributed transaction, failover & recovery, backup & restore.
• Online partition rebalancing, throttling & rate limiting.


• Product life cycle management
• Overseeing design, development, testing, deployment, operation, and monitoring.

Couchbase

• Key-value storage engine
  • Original author of ForestDB
  • Storage engine embedded in NoSQL server & mobile platform.
  • Optimizing file system and disk I/O patterns.

KAIST

• Index structures for block devices
  • Designing flash-optimized index structure for FTL (Flash Translation Layer) in SSD controller.

• Mobile/embedded device kernel
  • Designing lightweight encryption file system for Android platform.
  • Linux kernel optimization.

Publications and Patents

• Designing an Efficient Replicated Log Store with Consensus Protocol [PDF]
  Jung-Sang Ahn, Woon-Hak Kang, Kun Ren, Guogen Zhang, and Sami Ben-Romdhane
  USENIX HotCloud, 2019.

• Jungle: Towards Dynamically Adjustable Key-Value Store by Combining LSM-Tree and Copy-On-Write B+-Tree [PDF]
  Jung-Sang Ahn, Mohiuddin Abdul Qader, Woon-Hak Kang, Hieu Nguyen, Guogen Zhang, and Sami Ben-Romdhane
  USENIX HotStorage, 2019.

• GRIT: Consistent Distributed Transactions across Polyglot Microservices with Multiple Databases [PDF]
  Guogen Zhang, Kun Ren, Jung-Sang Ahn, and Sami Ben-Romdhane
  IEEE International Conference on Data Engineering (ICDE) (Demo), 2019.

• Session Guarantees with Raft and Hybrid Logical Clocks
  Mohammad Roohitavaf, Jung-Sang Ahn, Woon-Hak Kang, Kun Ren, Gene Zhang, Sami Ben-Romdhane, and Sandeep S. Kulkarni
  International Conference on Distributed Computing and Networking (ICDCN), 2019.

• Key-Value Replication with Consensus Protocol
  Sami Ben-Romdhane, Jung-Sang Ahn, and Guogen Zhang
  Patent No. 10838977 (December 26, 2019), United States.

• ForestDB: A Fast Key-Value Storage System for Variable-Length String Keys
  Jung-Sang Ahn, Chiyoung Seo, Ravi Mayuram, Rahim Yaseen, Jin-Soo Kim, and Seungryoul Maeng
  IEEE Transactions on Computers, 2016.

• Low-Overhead User Data Protection for Smartphones using Plaintext Cache
  Jung-Sang Ahn and Seungryoul Maeng
  Mobile Security Technologies (IEEE Symposium on Security and Privacy), 2013.

• μ*-Tree: An Ordered Index Structure for NAND Flash Memory with Adaptive Page Layout Scheme
  Jung-Sang Ahn, Dongwon Kang, Dawoon Jung, Jin-Soo Kim, and Seungryoul Maeng
  IEEE Transactions on Computers, 2013.

• Indexing Method for Flash Memory
  Jaesoo Lee, Jung-Sang Ahn, Jin-Soo Kim, and Dawoon Jung
  Patent No. 8799558 (August 5, 2014), United States.

• Indexing Method for Flash Memory
  Jaesoo Lee, Jung-Sang Ahn, Jin-Soo Kim, and Dawoon Jung
  Patent No. 10-1699779 (January 19, 2017), Korea.

Honors and Awards

• Third Place, ACM SIGMOD Programming Contest, 2012.
  
• Finalist, ACM SIGMOD Programming Contest, 2011.
  
• Bronze Prize, Samsung Humantech Paper Award, 2008.
• Silver Prize, Samsung Humantech Paper Award, 2004.
• Honorable Mention, Samsung Humantech Paper Award, 2003.
• Finalist, Intel ISEF (International Science and Engineering Fair), 2002.
• Gold Medal, KOI (Korea Olympiad in Informatics), 2001.

Services

• Journal paper referee, ACM Transactions on Storage, 2020.
• Program committee, Scalable Cloud Data Management (IEEE Big Data), 2020.
• Program committee, Scalable Cloud Data Management (IEEE Big Data), 2019.
• Program committee, Scalable Cloud Data Management (IEEE Big Data), 2018.
• Journal paper referee, ACM Transactions on Storage, 2017.
• Journal paper referee, IEEE Transactions on Computers, 2015.
• Journal paper referee, IEEE Transactions on VLSI Systems, 2014.
• Journal paper referee, IEEE Transactions on Computers, 2013.
• Journal paper referee, IEEE Transactions on Computers, 2012.

Contact

• E-mail: jungsang . ahn [at] gmail . com