How Redis’s Founder Defied Database Rules to Build the World’s Top In‑Memory Store

Redis has become one of the world’s most popular databases, a success rooted in founder Salvatore Sanfilippo’s willingness to break established database engineering rules because of his own lack of experience.

After ten years working on Oracle and SQL Server, Sanfilippo quit his job in 2009 to pursue his own dream. As a newcomer to databases, he began writing Redis, an in‑memory data store that challenged the conventional wisdom of the time.

Today companies such as Uber, Instacart, Slack, Hulu, Twitter and Instagram rely on Redis, yet Sanfilippo never tells developers how to use it; he believes the advantage of Redis comes from developers knowing how to apply it to their own problems.

The interview explores how Sanfilippo created this enterprise‑grade open‑source component and what motivated him.

Before Redis, Sanfilippo contributed to security tools like hping and the Idle Scan port‑scanning technique, built a blog analyzer called Visitors, created the Jim interpreter for Tcl, and wrote various device drivers.

He also worked on a real‑time analytics service, lloogg.com, trying to scale it with MySQL. The hardware requirements for ten‑thousand users proved impractical, leading him to adopt an in‑memory approach and ultimately to start Redis.

Redis was designed as an in‑memory NoSQL database that serves both as a data store and a cache, deliberately breaking many “sacred” database rules.

Traditional database experts criticized Redis for its memory limits, its use of fork for persistence, and its SHA‑1‑based Lua scripting model. While some criticisms were valid, they missed the broader direction of future databases.

Sanfilippo emphasizes open‑source innovation and sharing, tracing his own journey back to installing Slackware at age 18, discovering a C compiler, and recognizing that software development starts with open‑source collaboration.

He views software as a human‑centric activity that tells stories; as the Redis story spread, the community embraced it first in open‑source circles and later in large enterprises.

Although he welcomes community contributions, Sanfilippo acknowledges that good and bad ideas coexist, and contributing to a serious database system is demanding.

Over the past decade, Sanfilippo worried about Redis’s success and funding, but those concerns have largely resolved as Redis’s popularity grew. He now works at Redis Labs, still focusing on Redis rather than prescribing its use.

Redis can act as a primary database, an index for other databases, a smart cache, a messaging system, and more, thanks to its modular design that lets developers extend it creatively.

Sanfilippo does not see himself as an authority; he prefers designing new things and writing code, leaving it to developers to decide whether they become the “queen” or “king” of their applications.