Jung-Sang Ahn's Personal Website

Jung-Sang Ahn

안정상 (in Korean)

Interests

Indexing systems, file systems, storage systems, operating systems, embedded 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.

Experiences

eBay

Main developer of distributed database core engine
- Eventually/strongly consistent replication engine based on Paxos, Raft, and variants.
- Active-active (multi-master) conflict resolution logic.
- Distributed key-value store, log store, and global secondary index, across geo-distributed multiple data centers.

Couchbase

Key-value storage engine
- Original inventor of ForestDB
- Development of storage engine for NoSQL server & mobile platform.
- Optimizing file system and disk I/O patterns.
- Designing efficient index structures.

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

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
ACM 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.

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