One thing that has always made me curious is how online games are able to process in real-time really novel or unique achievements and instantly give you a badge.
Simple things like get 10 kills or finish a level seem easy enough, but things like kill someone by shooting every bullet in your clip into one person while jumping - or something like that seems pretty crazy to program.
Do they just have a big processor that reads through real time logs of all activity and is constantly calculating every achievement - or is achievement programmed into the game itself, into the very game logic? It seems like the latter wouldn't be the case since new achievements for games come up fairly frequently.
Is there a well-established pattern or architecture for this kind of thing?