This might of course introduce quite a bit of overhead, but the clean solution would arguably be to not mix requests to begin with, the external requests you are processing are the payload of the requests you are sending around internally. This would also allow you to cook up an optimized encapsulation protocol that might be more efficient to process than parsing and modifying HTTP. This admittedly comes from someone with essentially zero knowledge of what exactly Cloudflare is doing to the requests they receive.