The Legend of Alibaba’s Solo Engineer: How ‘Duo Long’ Built Core Systems Alone

In Alibaba’s final pre‑IPO prospectus update in 2014, three new partners were listed, one of whom was Cai Jingxian, nicknamed “Duo Long.” Within Taobao, he earned titles such as “god,” “the greatest among greats,” and “Shaolin sweeping monk.”

The author joined Alibaba in September 2013, worked in Duo Long’s team for a year, and shares personal observations. Duo Long’s academic background is in life sciences, not computer science, yet he rose to a P11 technical position—equivalent to vice president.

His team was tiny: only three direct reports, one of whom was based in Beijing. Duo Long preferred minimal team interaction; he believed a single person could match the output of an entire high‑efficiency team. He single‑handedly developed and maintained early Taobao products, including the file system TFS, the key‑value store Tair, caching, search, and communication frameworks.

Colleagues called him a “god” on the internal network, not as flattery but because he could build a whole project alone—writing a file system that would normally require an entire team or company. From 2003 to 2007, he alone wrote and maintained Taobao’s search engine, among many other responsibilities.

Duo Long avoided socializing and rarely appeared in public. He often worked on a laptop even during outings, writing code at any opportunity. He described his interest as simply writing code, spending fourteen years doing nothing but coding during work hours.

He attributes his knowledge growth to the diverse problems encountered during Taobao’s rapid development. He treats every problem as worth solving and every technology as worth learning, absorbing new knowledge like a sponge. For each new concept, he writes a piece of code to verify and deepen his understanding.

When faced with a complex feature, he once arrived at the office at 4 a.m. after an overnight insight and immediately began implementation, constantly seeking performance improvements.

He is praised as “smarter and harder‑working than anyone.” When asked how he became a legend, he replied, “Just solve problems,” ranging from early PHP issues to cutting‑edge performance challenges. His fourteen‑year focus, combined with Taobao’s fast growth, turned simple problem‑solving into mastery.

His technical philosophy reaches a state of “no sword in hand, sword in heart.” He solves problems without ready answers by reading source code—from glibc to the kernel—often mastering technologies before anyone else.

His nickname “Duo Long” originated from a colleague named Xiao Bao, who would say “Ask the chief, Duo Long,” whenever a problem arose; the name stuck, and even today, people still seek his help for unsolvable issues.

In summary, Duo Long exemplifies comprehensive technical depth, unparalleled focus, responsibility, and a true craftsman spirit—earning him the legendary “god” title within Alibaba.