I assume the issue is interactive lookup access time.

Reloading the DB dump you receive into a local DB, as Flech suggests, is the best option, but if you can't afford to set up a database server, then your only other choice, is to use something like Search::Binary, and implement it's read() function using seek. It wouldn't be as fast in searching, but it might be acceptable, and way better than linear search which would take a long time on a file that size, even with a very big disk cache. Other than DB or binary search, trying to squeeze it into memory is your only only option, and storing it as strings with separators and/or with some compression is the thing to try.

On the other hand, if you have a batch process, with a list of keys (pins), you can do an fgrep against the full file with the list of pins, if it isn't too big, and then pipe that into a hash.