Relying on http has the advantage that you can leverage commodity infrastructure like caching proxies and CDN.
Why push protobuf over http when all you need is present in http already?
If moving big files around is a major part of the system you’re building, then it’s worth the effort. But if you’re only occasionally moving big files around, then reusing your existing gRPC infrastructure is likely preferable. Keeps your systems nice and uniform, which make it easier to understand later once you’ve forgotten what you originally implemented.
also, http/s compatibility falls off in the long tail of functionality. i've seen cache layers fail to properly implement restartable http.
that said, making long transfers actually restartable, robust and reliable is a lot more work than is presented here.
These would be the ultimate in resumability and mobility between networks, assuming that they exploit the protocol to the fullest.
Still, stateful protocols have a tendency to bite when you scale up. And HTTP is specifically designed to be stateless and you get scalability for free as long as you stick with plain GET requests...
If you happen to be on ASP.NET or Spring Boot its some boilerplate to stand up a plain http and gRPC endpoints side by side but I guess you could be running something more exotic than that.
feel free to put them both behind load balancers and see how you go
For example, there are common metadata such as the digest (hash) of the blob, the compression algorithm, the base compression dictionary, whether Reed-Solomon is applicable or not, etc...
And like others have pointed out, having existing grpc infrastructure in place definitely helps using it a lot easier.
But yeah, it's a tradeoff.