Software Optimisation Never END – Asymmetric Load Balancing Algoritm, Review

2 years ago, I published a PHP solution on the blog for choosing the right server from a servers list, based on the available bandwidth configured: Asymmetric Load Balancing Server Solution.

The algorithm can be used in Load Balancing proxy servers, for CDNs as well as for any other needs where a balanced distribution of resources is required;

Recently I am working on a cache plugin written in PHP, developed for any kind of web pages (non CMS) as well as for Wordpress: page, object and database.

You must be wondering why I don’t choose a plugin that is already free?

Because most of them are too complex, and they have long lost their perspective on simplicity, utility and performance!

And when I came to the implementation of a solution for CDN, I remembered the php function published over 2 years ago … but after so long it seems that my brain has advanced more in the optimization segment, the old solution seemed to me “heavy”.. So after less than 5 minutes I realized that the method of choosing a server was still very good, but there was still room for optimization!

So, below is a new version for Asymmetric Load Balancing Server, much faster and even simpler!


$config_cdn = [
  '' => 10,  
  '' => 30,
  '' => 60,

# server config as [hostname => number], where number is bandwidth or a load percentage; 
# 10,30,60 can be 1,3,6 or 100,300,600, it's all about keeping the ratio between numbers.

/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
function getAsym_LB_ServerV2(&$config_cdn) {

  $server_rand = mt_rand(1, array_sum($config_cdn));
  $segment_bandwidth = reset($config_cdn);

  foreach ($config_cdn as $server=>$bandwidth) {
    if ($server_rand <= $segment_bandwidth) {
    $segment_bandwidth += $bandwidth;

  return $server;

/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */

echo getAsym_LB_ServerV2($config_cdn);

Execution speed tests performed in PHP 7.4.2 showed that the above version is 40% faster than the one published 2 years ago.

Conclusion: Software Optimization Never END!

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