TIL: Per the article, this 256 limitation also applies to number of users in WhatsApp conversations and the maximum block height of a Minecraft world.
(Max value in java, even though the game is non longer written in Java)
Java (and other languages) have other ways of representing numbers which allow larger values, but once you've encoded values into wire protocols and persistent data structures, they tend to be hard to change.
But that limitation makes no sense for WhatsApp user limit count. Presumably every user has an id number identifying them (maybe a long integer). You need to maintain a list of these users so your array is already way larger than 8 bits.
Can someone intuit why the 256 limit in WhatsApp?