Well, besides pgloader, which achieved a 20~30x speedup via a rewrite from Python to Common Lisp (<https://tapoueh.org/blog/2014/05/why-is-pgloader-so-much-fas...>), there is also this little organisation called NASA which has a collection of theorem proving libraries called variously PVSLib or NASALib (<https://github.com/nasa/pvslib>).

There is a lot more as well, of course, but these two are clear examples of Common Lisp being used in 'the real world'.