Oh, they will have different systems but postal codes are widespread and where they aren't you can find other alternatives - when a country hits a certain level it needs bureaucratic divisions to ensure everything can be parcelled up and administration devolved. These tend to run on population density as it means that no one area is overwhelmed.

If you rolled out to North America, Europe and Australia/New Zealand (and probably most former British Empire countries as this became a problem in the 19th Century) you could then get good coverage using postal codes and then look at how the other countries do it.