The next step is to enable more post-invalidation precompile for Plots. This is something we recently setup with Symbolics.jl since that is another package which has some "invalidation by design" patterns, where certain assumptions made in the compiler (such as (x==y)::Bool) are invalidated by symbolic numbers acting differently than a lot of numbers and thus some over-eager optimizations require being removed upon using. PrecompileTools.@recompile_invalidations is a recent (v1.9 era) tool that allows for forcing the compile at package precompile time to consider the environment post-invalidation and thus re-precompile, effectively reducing the TTFX in these cases where invalidation is always going to occur by design. Plots.jl is a case like this because its recipe system is effectively allowing people to extend the plotting pipeline well after Plots is loaded, which is its main killer feature but effectively means that one should expect invalidations from it. I think that recompilation post invalidation should make a strong dent in that and plan to see if that's the case in a few months when I get the time to dive in.

> Wouldn't something like slow interpreter option for "glue code" be feasible? Most code doesn't need to be fast, and waiting for the "hot functions" to compile on change wouldn't be too bad. And you could still AOT for maximum speed when needed. This is essentially how Javascript JITs manage to start up so fast.

That is something I've been meaning to investigate more. A lot of the Plots.jl code is internally dynamic because of its design to hold everything in a Dict{Any} and recurse the plot recipes. In other words, it doesn't even benefit from having the JIT at all because internally everything is uninferred boxed variables. There's probably a good way to just do "please interpret the calls in this part of the pipeline" and not see any runtime difference but chop out the core of the compilation. It's relatively straightforward to do, it's a one liner using JuliaInterpreter.jl @interpret, and I think one dig that results in a win would be a nice example of what should be a pattern we do more often in the near future.