Fastpack stores some valuable data about the project structure, filesystem and
loaded modules in the persistent cache. This permits to improve the building
speed after the restart. The cache files reside in the
<project directory>/node_modules/.cache/fpack or
<project directory>/.cache/fpack if
<project directory>/node_modules does not exist.
Persistent cache is used in development mode only. If you want to disable cache for some reason - use the --no-cache flag. Alternatively, you may delete the cache directory entirely.
Fastpack uses the Marshal module to save/load the cache. Don't try to edit produced files manually, since it may follow to Segmentation fault errors.