API Gateway is closed source for one. Kong is written in Lua, for better or worse.
Lua per-se is a fast language (having a very small footprint), but running Lua on top of LuaJIT [1] is just so much faster. LuaJIT is an alternative implementation of the Lua VM created by Mike Pall and now supported by a few other folks and organizations like Cloudflare. Cloudflare in particular has a very large runtime implementation of the Lua + LuaJIT stack, and usually people are surprised to learn that at least 10% of the worldwide Internet traffic [2] goes through this stack.
With that said Lua + LuaJIT is being used in other applications as well, like mobile and embedded devices, where low footprint and high performance are required.
Having a low footprint is not just a nice-to-have, but a requirement for running a proxy in a Service Mesh deployment as a decentralized sidecar container (to not exhaust all the resources of the underlying VMs as we scale the number of pods and services) in addition to the traditional centralized API Gateway deployment.
You found some very low hanging fruit in the JIT engine in particular (64 global trace buckets), fixed it and at least threw it over the fence upstream (and kudos for that). But you buried it in a bunch of irrelevant figures, and at the end of the article you rediscovered GC pauses. GC pauses are a classic, well-known problem with GC languages.
My critiques are this:
1. There is a huge body of prior work and analysis of JIT'd and GC languages due to the outsized impact of Java, probably the most popular language on the planet at one point (if it isn't still). (And Golang — Java 2.0.) Java's history (and perhaps Golang's more recent history) should have been top-of-mind at the outset of this project. I think you could continue to apply lessons learned from abundance of experience around Hotspot and JRE tuning to the LuaJIT interpreter.
2. The lengthy benchmark spreadsheets seem like a distraction rather than a useful tool. They're certainly not adding much to the article and could be summarized in 2-3 sentences each. If you really felt like it, they could be linked to an external appendix.