Ease/ability to embed in other language safely. Predictability of memory, execution. Known constraints like guaranteed to terminate is useful.

no Doom running on cel.

I recently wanted to expose some basic user auto tagging/labeling based on the json data.

I chose cel, over python, SQL because I could just import the runtime in C++, or any language that implements it (python, js etc..)

Safely running a sandboxed python execution engine is significantly more effort and lower performance.

At this cel excels.

Where it didn't was user familiarity and when the json data itself was complex.

> Known constraints like guaranteed to terminate is useful.

"Guaranteed to terminate" actually means "guaranteed to terminate in finite but possibly arbitrarily large time" which is really not a useful property.

There's no practical difference between a filter that might take 1 billion years to run and one that might take more than a billion years.