I haven’t used Genie (though after this post I am tempted!) but I imagine compilation overhead would only occur once (e.g. the first time each route is used) and that you could pretty easily use precompile statements and/or PackageCompiler.jl to do the compilation before the service goes live. After that point, Julia should have produced fast code and provides a good runtime for these kinds of async/multithreaded applications with built-in M:N scheduling (perhaps a concurrent/multithreaded GC might help reduce tail latency but I imagine it should already be competitive with everything but well-written Rust/C++/C).