Forget memoised World Bank fetches, both in-session and (optionally) on disk.
Where the cache lives
The persistent cache goes in the standard per-user cache location,
tools::R_user_dir("countryatlas", "cache"). Point it elsewhere with
options(countryatlas.cache_dir = ), or skip the disk entirely by passing
cache = FALSE to world_data() / country_data(). The directory itself is
created the first time a cached fetch is attempted, whether or not the World
Bank answers; only a successful fetch leaves a response in it, and reading the
bundled world_snapshot never goes near it. Under R CMD check the whole
cache moves to the session temp directory, so a check never writes to the
user's file space.
How the cache is managed
The persistent cache expires its own contents, so it does not grow without
bound and does not serve stale figures indefinitely: an entry is dropped
once it is 30 days old, and if the directory exceeds 50 MB the
least-recently-used entries go first. Both limits are adjustable with
options(countryatlas.cache_max_age = ) (seconds) and
options(countryatlas.cache_max_size = ) (bytes). A dropped entry costs a
re-fetch, nothing more.
Expiry matters beyond disk space: World Bank observations are revised, so a figure cached long ago is not necessarily the figure the API would return today.