Juncheng Yang Winner of ACM Award for Dissertation with Most Impact

Juncheng Yang, assistant professor of computer science in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), received the Dennis M. Ritchie Doctoral Dissertation Award from the Association of Computing Machinery (ACM). The award recognizes outstanding doctoral research in operating systems and related areas.

Yang, who joined the SEAS faculty this year, was honored for his doctoral thesis titled “Designing Efficient and Scalable Key-value Cache Management Systems,” completed during his Ph.D. work at Carnegie Mellon University. The award is given annually by the ACM Special Interest Group in Operating Systems at the international Symposium on Operating Systems Principles, held earlier this month.

Yang’s research focuses on performance, sustainability and reliability of data systems. His award-winning thesis examined the efficiency and scalability of caching – a ubiquitous process that stores frequently accessed data in small, fast memory systems so that future requests can be served quickly. Software caches in phones, laptops and cloud data centers consume vast resources, for example, petabytes of dynamic random-access memory in a single Google caching service.

Yang’s thesis described two large measurement studies that uncovered new insights and produced several major advances in the field. One innovation, called Segcache, is an in-memory key-value cache that significantly reduces resources for workloads that have small objects and use the mechanism known as time-to-live, which limits the lifespan of data in a network. This work received the 2021 Networked Systems Design and Implementation Community Award.

The thesis also describes two caching algorithms, S3-FIFO and SIEVE, which are simpler than state-of-the-art approaches and improve efficiency and scalability. Winning the 2024 Networked Systems Design and Implementary Community Award, they represent a profound shift in the field from LRU-centric (Least Recently Used) to FIFO-centric (First In, First Out) designs. These algorithms have seen broad industry adoption — including in Android, the TiDB database, and many others — and have been implemented in dozens of open-source systems and libraries, including over 60 across more than 16 programming languages on GitHub.

Established in 2013, the ACM Dennis Ritchie dissertation award honors the eponymous UNIX and C pioneer. It recognizes an outstanding dissertation that advances software systems, embodies creativity and impact, and highlights how a single researcher’s work can significantly move the field forward.