When compressed sizes can still matter as the payload size increases. REST is the language the rest of the web speaks so if providing a consumer service that i

When compressed sizes can still matter as the payload size increases. REST is the language the rest of the web speaks so if providing a consumer service that isn't latency sensitive you should feel at liberty to give a RESTful API. If you're building internal services, consumed internally, gRPC is a decent way to go. If say you're providing a logging service to a number of large customers you might want to provide a gRPC service for the performance characteristics. gRPC also provides you the option to write all your services internally using gRPC and then you can expose a JSON service without having to write it yourself.