OceanBase Internals: Transactions, Replay, SQL Engine, and Unit Placement

Why These Paths Matter OceanBase targets high availability and scalability in a shared-nothing cluster. The core engineering challenge is to make four critical subsystems work together with predictable latency and correctness: Write transactions must be durable, replicated, and efficiently committed. Tablet replay must recover state quickly and safely. SQL parse to execute must optimize well while respecting multi-tenant constraints. Unit placement must map tenants to physical resources without fragmentation. This article focuses on motivation, design, implementation highlights, and tradeoffs, using concrete code entry points from the OceanBase codebase. ...

January 17, 2026 · 8 min · 1517 words · Jack Yu

Understanding the CAP Theorem

Background The CAP theorem has become one of the hottest theorems in recent years; when discussing distributed systems, CAP is inevitably mentioned. However, I feel that I haven’t thoroughly understood it, so I wanted to write a blog post to record my understanding. I will update the content as I gain new insights. Understanding I read the first part of this paper. The CAP theorem [Bre12] says that you can only have two of the three desirable properties of: ...

December 20, 2017 · 3 min · 511 words · Jack Yu