[nattaylor]

A friend built a system where the ad campaigns with all their targeting rules were Lua scripts and it was also fast and simple in a glorious way!

[ing33k]

I tried a similar approach with a team I was working with. We were building it on top of redis and after some basic benchmarks gave up the idea and figured out from the docs that that eval script is blocking.

[bastawhiz]

Lua in Redis is not useful for serving as a runtime for running Lua application code; it's valuable for allowing you to perform a series of steps atomically. You can read and write data without worrying about something else changing: only one piece of code can write at a time. We use it for rate limiting, which requires reading and writing atomically, for instance.

[btilly]

When I did that on a project I solved that problem by replicating redis to the same container that the ads were being served from. Replication was very fast, and all that was blocked was the local redis. I worked to make the matching rules in the script efficient, and the blockage was truly not a problem.

[knighthack]

Why wasn't Python used? I imagine for such a use case it wouldn't be that much heavier to use Python vs Lua.

[catlifeonmars]

Integration complexity could be a factor. I’m making an assumption about the architecture, but embedding Lua in a program is dead simple and you can do so without introducing external dependencies. Python IIRC requires you to ship and package the standard library or have it already installed, the Lua interpreter can be statically embedded in a program.

[qwertox]

Speed, probably. Lua is much faster.