That said, I actually posted my query on the memcache mailing list and discovered several things. The entire thread is at http://bit.ly/lnfiuv. The major takeaway was that Cache::Memcached was way to slow. Per "Dormando's" suggestion, I installed Cache::Memcached::libmemcached and memcached code actually became about 30% faster than pure SQLite code. I also modified my test to get_multi IDs, as I learned that network travel is just a lot slower than disk travel. Here is the result --

Benchmark: timing 10000 iterations of query_dbh, query_mem...
 query_dbh:  6 wallclock secs ( 3.87 usr +  0.92 sys =  4.79 CPU) @ 20
+87.68/s (n=10000)
 query_mem:  6 wallclock secs ( 2.51 usr +  1.23 sys =  3.74 CPU) @ 26
+73.80/s (n=10000)
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For the record, here is my complete test script, including the code for creating the test db.

#!/usr/local/bin/perl

use strict;
use Cache::Memcached::libmemcached;
use DBI qw(:sql_types);
use Benchmark qw(:all);

my $dbh = DBI->connect(
    "dbi:SQLite:dbname=mem.sqlite","","", 
    {RaiseError => 1, AutoCommit => 0}
);

my $memd = new Cache::Memcached::libmemcached ({
    'servers' => [ "localhost:11212" ]
});

my $sql = "SELECT Ifnull(str, 'none') FROM t WHERE id = ?";
my @ids = map { int(rand(19_999)) || 1 } (0 .. 20);

timethese(10_000, {
    'query_mem' =>  sub {
        my $hashref = $memd->get_multi(@ids);
        
        my @res = ();
        while (my ($id, $str) = each %$hashref) {
            unless ($str) {
                my $sth = $dbh->prepare($sql);
                $sth->execute($id);
                ($str) = $sth->fetchrow_array;
                $memd->set($id, $str);
            }
            
            push @res, [$id, $str];
        }
        out(@res);
    },
    'query_dbh' =>  sub {
        my $sth = $dbh->prepare($sql);
        
        my @res = ();
        for (@ids) {
            $sth->execute($_);
            my ($str) = $sth->fetchrow_array;
            push @res, [$_, $str];
        }
        out(@res);
    },
});

sub out {
    my @res = @_;
    
    open F, ">", "foo.txt" or die $!;
    say F "id: " . $_->[0] . ", str: " . $_->[1] for (@res);
    close F;
}

sub create_db {
    my $sth = $dbh->prepare(
        "CREATE TABLE t (id INTEGER PRIMARY KEY, str TEXT"
    );
    
    $sth->execute;
    $dbh->commit;
}

sub pop_db {
    my $sth = $dbh->prepare("INSERT INTO t (str) VALUES (?)");
    
    $sth->execute(randstr(rand(100))) for (0 .. 20_000);
    $dbh->commit;
}

sub randstr {
    my $len = shift;

    my @chr = ('a'..'z','A'..'Z','0'..'9','_', ' ');
    return join "", map { $chr[rand @chr] } 1 .. $len;
}
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