I once worked on a rather convoluted bunch of microservices where 40% of CPU time was spend inside cJSON library. Cap'n Proto does exactly what you propose - se

I once worked on a rather convoluted bunch of microservices where 40% of CPU time was spend inside cJSON library. Cap'n Proto does exactly what you propose - sends bytes over, except in a documented, organized, forward- and backward-compatible manner, instead of a haphazard implementation burdened by technological debt.