“One of the brightest; one of the best! I had the opportunity to work with YJ for many years at Facebook. On that journey, YJ transitioned from a high-performing senior engineer to an engineer manager and quickly grew as an org leader. He was a mature, competent, and trusted partner. YJ has a knack for solving tough problems, including technical, people, and organization problems. We share the values of doing things the right way: for the org but also caring for the people, with high level of transparency, and fun. I miss working with YJ and hope our paths will cross again in the future!”
Activity
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I did a deep dive for those of you who are wondering who is going to win the AI race. 🏇 🐎 🏇 🐎 Is Anthropic really the leader in the…
I did a deep dive for those of you who are wondering who is going to win the AI race. 🏇 🐎 🏇 🐎 Is Anthropic really the leader in the…
Liked by Yee Jiun (YJ) Song
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After a few seasons at the ‘book, it’s time to try something new. Facebook has been an incredible place to develop. Per custom upon departure, I…
After a few seasons at the ‘book, it’s time to try something new. Facebook has been an incredible place to develop. Per custom upon departure, I…
Liked by Yee Jiun (YJ) Song
Experience & Education
Publications
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Existential Consistency: Measuring and Understanding Consistency at Facebook
SOSP
See publicationReplicated storage for large Web services faces a trade-off between stronger forms of
consistency and higher performance properties. Stronger consistency prevents anomalies,
i.e., unexpected behavior visible to users, and reduces programming complexity. There
is much recent work on improving the performance properties of systems with stronger
consistency, yet the flip-side of this trade-off remains elusively hard to quantify. To the best
of our knowledge, no prior work does so…Replicated storage for large Web services faces a trade-off between stronger forms of
consistency and higher performance properties. Stronger consistency prevents anomalies,
i.e., unexpected behavior visible to users, and reduces programming complexity. There
is much recent work on improving the performance properties of systems with stronger
consistency, yet the flip-side of this trade-off remains elusively hard to quantify. To the best
of our knowledge, no prior work does so for a large, production Web service.
We use measurement and analysis of requests to Facebook’s TAO system to quantify
how often anomalies happen in practice, i.e., when results returned by eventually consistent
TAO differ from what is allowed by stronger consistency models. For instance, our analysis
shows that 0.0004% of reads to vertices would return different results in a linearizable
system. This in turn gives insight into the benefits of stronger consistency; 0.0004% of reads
are potential anomalies that a linearizable system would prevent. We directly study local
consistency models—i.e., those we can analyze using requests to a sample of objects—and
use the relationships between models to infer bounds on the others.
We also describe a practical consistency monitoring system that tracks φ-consistency,
a new consistency metric ideally suited for health monitoring. In addition, we give insight
into the increased programming complexity of weaker consistency by discussing bugs our
monitoring uncovered, and anti-patterns we teach developers to avoid.
Languages
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English
Native or bilingual proficiency
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Chinese
Professional working proficiency
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