Jung-Sang Ahn

안정상 (in Korean)

Software Engineer at eBay.
LinkedIn
Github

Interests

• Indexing, caching, replication, key-value store.
• Distributed systems, storage/file systems, operating systems.
• Problem solving, optimizing performance.
• Electric/acoustic guitar, finger-style guitar, band session, song writing, recording/mixing/mastering.
• Snowboarding, go-kart.

Employment and Education

• Member of Technical Staff, Distributed Systems, eBay, 2017 - present.
• Senior Software Engineer, Couchbase, 2015 - 2017.
• Ph.D. in Computer Science (Computer Architecture Lab.), KAIST, 2010 - 2015.
• M.S. in Computer Science (Computer Architecture 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.

Experience

  eBay

• Lead developer of distributed database core engine
  • Sync / async replication engine: Paxos, Raft, and variants.
  • Storage engine embedded in each node: B+tree, LSM-tree, append-only logs, and variants.
  • Active-active (multi-master) conflict resolution logic.
  • Distributed key-value / log / global secondary index store across multiple data centers.

  Couchbase

• Key-value storage engine
  • Original inventor 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.

Personal Projects

• Generic lock-free Skiplist container
  
  • Pure C-style container based on Skiplist, supporting any type of data.
  • Lock-free: multiple readers and writers.

• Generic AVL-tree container
  
  • Pure C-style container based on AVL-tree, supporting any type of data.
  • Up to 3x faster than STL set or map.

• Test Suite
  
  • Lightweight (a single header file) test suite for C++ program.

• Simple Logger
  
  • Lightweight and lock-free logging library for C++ program.

• Latency Collector
  
  • Lightweight embedded library to measure latencies of C++ program.

• Hex Dump

Publications and Patents

• Designing an Efficient Replicated Log Store with Consensus Protocol
  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
  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
  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 Filed (2018), 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.
  A Multi-Dimensional Indexing System
• Finalist, ACM SIGMOD Programming Contest, 2011.
  A Durable Main-Memory Index Using Flash
• 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

• Program committee, Scalable Cloud Data Management (IEEE Big Data), 2018.
• Journal paper referee, ACM Transactions on Storage, 2017.
• 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 Information

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