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APT Cache File Format
Chapter 4 Future Directions

Some good directions to take the cache file is into a cache directory that contains many associated caches that cache other important bits of information. (/var/cache/apt, FHS2)

Caching of the info/*.list is an excellent place to start, by generating all the list files into a tree structure and reverse linking them to the package structures in the main cache file major speed gains in dpkg might be achieved.