Have a look at: Speeding up the DBI, it contains valuable information about DBI, and about what methods to use.
example from this page (since you want to query large amounts of data):

$sth->execute; # dataset has 1,000,000 records
#
# DON'T DO THIS
# my $aref = $sth->fetchall_arrayref;
#
# It would create a 1,000,000 rows array

my $max_rows = 5_000;

while (my $aref = $sth->fetchall_arrayref(undef, $max_rows))
{
    # do something with $aref
    # $aref now contains (at most) 5,000 rows
};
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