Comment by cloudflare

From the post:

    A recent example illustrates the power of this approach:

    Cloudflare's WAF (web application firewall) basically generates
    Lua code for the (highly non-linear) maze of firewall rules. An
    incoming attack triggers certain rules and the corresponding paths
    are turned into linearized traces. These can be heavily optimized
    by LuaJIT, much more so than you could ever hope to do with a
    static compiler.

    When a different attack wave is started, it'll spawn different
    traces -- i.e. the generated code dynamically adapts to the
    specific attacks.

    The result is a much higher firewall throughput than you might be
    able to achieve with a data-driven or a static compilation
    approach. This directly equates into money saved on machines
    needed to handle the load.

Added to that is the fact that the WAF configuration (which is automatically generated Lua code) is different for each customer and so we rely heavily on caching and JITing to get the performance.

The bottom line is that LuaJIT is very fast and very flexible.