IMHO, it doesn't need to be overly complicated, but I might be wrong. The optimizer doesn't have to optimize all the Clojure code out there (for the start). Still, it could adopt a Graalvm-like approach, explicitly stating which elements the optimizer can optimize and encouraging developers to write their code accordingly. Alternatively, it can go with CL "declare"-like construct [1], allowing developers to explicitly insert hints for the optimizer.

[1] https://www.lispworks.com/documentation/HyperSpec/Body/s_dec...