I was tinkering with a react-native app the other day which shows a map and lets the user click on …

… I was tinkering with a react-native app the other day which shows a map and lets the user click on a building, and then highlights the building and shows some information. There was a noticable delay after clicking which made it not much fun to use. So I spent a couple evenings (hobby time, not company time) to integrate a proper spatial database with a fast spatial index, precache a lot of data, so I didn't have to hit the network. It got snappier, I could query a lot of geometry much faster, but it still felt slow. Then I looked into the source of the libraries, and in some react-native glue code I found that the event handler was waiting after the first tap for a double-tap, and thus would only register the tap after a couple hundred ms. One tiny change and it became blazing fast. I believe most apps could do most things instantaneously. Google can find any document on the net in a few ms, after all. But of course not everybody has the time and money (or even skills) to polish their apps that much. …