Because they're typically running locally they're quick, or at least as quick as your hardware will allow. The json-related latency is typically dwarfed by the

Because they're typically running locally they're quick, or at least as quick as your hardware will allow. The json-related latency is typically dwarfed by the latency from actually doing the functionality (parsing the code for code completion, etc). So the real work is in having a good story for incremental compilation and a generally quick and robust compile toolchain. I guess that Go is in a good position here ...