SHELL = /bin/bash

.PHONY: data
data:
	for i in {1..10} ; do for j in {1..10} ; do echo "[$$i,$$j,$$RANDOM]" > $$i-$$j.json ; done ; done

.PHONY: simulate_cron
simulate_cron: data
	while : ; do \
		i=$$((1 + RANDOM % 10)) ; j=$$((1 + RANDOM % 10)) ; echo "[$$i,$$j,$$RANDOM]" > tmp ; mv tmp $$i-$$j.json ;\
	done

.PHONY: query
query:
	time perl query.pl

.PHONY: clean
clean:
	rm -f *.json

##</code><code>##

make simulate_cron

##</code><code>##

make query

##</code><code>##

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Cpanel::JSON::XS qw{ decode_json };

my %cache;
for (1 .. 1000) {
    my @queries = map [ map int 1 + rand 10, 1, 2 ], 1 .. 50;
    for my $query (@queries) {
        my ($x, $y) = @$query;

        # delete $cache{$x}{$y};  # <- Uncomment to simulate no cache.

        my $value;
        if (exists $cache{$x}{$y}
            && (stat "$x-$y.json")[9] == $cache{$x}{$y}{last}
        ) {
            $value = $cache{$x}{$y}{value};

        } else {
            open my $in, '<', "$x-$y.json" or die $!;
            $cache{$x}{$y}{last} = (stat $in)[9];
            $value = $cache{$x}{$y}{value} = decode_json(do { local $/; <$in> })->[2];
        }
        say "$x, $y: $value";
    }
}