As an abstract statement, I can only agree. In reality, modern compilers can do some incrementally. So when you make a change in file A, the compiler will only

As an abstract statement, I can only agree. In reality, modern compilers can do some incrementally. So when you make a change in file A, the compiler will only change things dependent on A. In practice this chains a small number of file recompiles. The end result is an instantaneous feedback loop. I get this all the time in Eclipse. Eclipse doesn't really try to do a full compile. It just updates as above. This allows me to see within a few ms if my code compiles. If it doesn't, red line and the reason. A full compile on a about 40k classes without tests (just compile, static checking) with Maven on my 2013 MBP is about 5 seconds. So still pretty fast. Probably equivalently as a fast as your dynamic language + tests. The same is true for hot swapping code. The JVM supports this a bit. Spring Boot supports it more. JRebel supports it entirely. When making a micro service or even a website in Spring Boot STS (Eclipse + Spring features), the run time will restart. Clocked time is 1.2 seconds. Not too bad. For changes to just HTML/CSS/templates/ etc, no reboot time.