Forgive my improper terminology - I didn't take computer science, so I may be using terms incorrectly. I would definitely like to extend the module into a cache (which would include a callback to generate missing information), but I suppose that we're looking more at a database. My confused terminology actually comes from my investigation of Cache::Cache. The documentation uses the example:

  use Cache::FileCache;

  my $cache = new Cache::FileCache( );

  my $customer = $cache->get( $name );

  if ( not defined $customer )
  {
    $customer = get_customer_from_db( $name );
    $cache->set( $name, $customer, "10 minutes" );
  }

  return $customer;
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So, if our calling code is implemented similarly, then the database becomes a cache. (Generating 200MB tar.gz files off the network isn't free, but using already-built tarballs from the local drive is about as free as it's going to get.)

The way our code works now is that we start with a preparation phase, where the cache/database is populated with things that are going to be needed 1-15 times. Then we enter the execution phase where we pull items from the cache/database as needed to build what we need to build.

Note that we've also given thought to actually using an RDBMS rather than the filesystem to allow us different flexibilities - e.g., having multiple machines pull from the common cache via DBI. Or using FTP or HTTP as protocols to do similarly. The RDBMS idea is more of a coolness thing - FTP or HTTP are probably better (i.e., more practical) protocols for this.