"Insanely fast" was borrowed from the project that Serender is based on, which is Zombie (an insanely fast headless browser used for testing client side code).

"Insanely fast" was borrowed from the project that Serender is based on, which is Zombie (an insanely fast headless browser used for testing client side code). Now of course, the speed of rendering depends on how fast your client side code is. If it has some ajax calls that fetch some really heavy data, the rendering can take few more milliseconds, but it's still fast because there is a very low network latency and your database is surely on the same network as your application, if not on the same server! I'm claiming that it's "insanely fast" because creating a new headless browser instance takes nearly no time at all, so the speed totally depends on your client side code.