And replying further: this isn’t about whether FIX makes the right trade offs. This is about the fact that, even in the position in design space that FIX occupi

And replying further: this isn’t about whether FIX makes the right trade offs. This is about the fact that, even in the position in design space that FIX occupies, FIX is terrible. One could have easily designed a protocol with the same level of security as FIX and precisely the same (application) message semantics and schema that actually worked well. It wouldn’t even be very different from FIX. All you would need is proper layering, group delimiters, delimiters for entire messages, and either proper escaping or length-prefixing of fields. (And length-prefixing would make parsing quite a bit faster without needing to resort to vectorized searches for where fields and groups end.)