And then a C programmer comes in and slams sendfile. That’s the main advantage of HTTP/1.1. Of course TLS throws a wrench in it, but once kTLS is actually good (ahem), it’ll work.

In all seriousness, don’t do large file transfers over gRPC, except in a pinch for small files. As soon as e.g API gateways are introduced in the mix, stuff can go south very quickly: increased allocation, GC pressure, network usage, etc. Just use presigned S3 URLs.

S3 also gives you multipart parallel uploads. Each part gets stored and then when you're done the concatenation is performed close to the storage layer.