21CTO

Jan 28, 2019 · Databases

How Alibaba’s TDDL Evolved from Cobar to Power Billions of Daily Queries

This article traces the evolution of Alibaba’s distributed data layer—from the early Cobar system to the modern TDDL framework and DRDS service—explaining their architectures, limitations, sharding principles, transaction‑boundary strategies, heterogeneous index tables, and the Jingwei data‑replication platform that together enable seamless scaling and high‑performance SQL processing across thousands of databases.