{"id":33498,"date":"2017-12-18T14:36:42","date_gmt":"2017-12-18T20:36:42","guid":{"rendered":"https:\/\/wpengine.com\/?post_type=support&p=33498"},"modified":"2025-07-28T11:05:21","modified_gmt":"2025-07-28T17:05:21","slug":"php-workers-request-prioritization","status":"publish","type":"support","link":"https:\/\/wpengine.com\/support\/php-workers-request-prioritization\/","title":{"rendered":"PHP Workers and Request Prioritization"},"content":{"rendered":"

In this article we explain the unique way WP Engine handles request prioritization when there is too much uncached traffic for the PHP Workers to handle.<\/p>\n\n\n\n\n\n<\/a>\n\n\n\n

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PHP Workers<\/h2>\n\n\n\n

Each uncached page request to your website is handled by a PHP Worker<\/strong><\/i><\/b>. You can think of these PHP Workers as cashiers in a store: each cashier handles one customer at a time, just as each PHP worker executes the PHP code that makes up a web page when a request comes in.<\/p>\n\n\n\n

Due to WP Engine\u2019s proprietary multi-tiered Evercache\u00ae system, many page requests are served from cache<\/a> and therefore many requests are not<\/strong> handled by a PHP worker. Serving a request from cache would be like a customer who comes in to pick up an order that\u2019s already been completed. It\u2019s fast and efficient, and doesn\u2019t burden the cashiers who need to be available for new customers and their unique orders.<\/p>\n\n\n\n

When every cashier is occupied with a transaction, a queue of waiting customers is formed. Similarly, when the PHP workers can\u2019t finish requests more quickly than they\u2019re coming in, a backlog is created.
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WP Engine Queuing Benefits<\/h2>\n\n\n\n

Where most hosts simply serves all traffic on a \u201cfirst come, first served\u201d basis, WP Engine understands that your site needs to reach real<\/em> users first. On WP Engine, our unique traffic shaping system prioritizes real users above requests from bots, crawlers, and AJAX<\/a> requests. That means your site will always serve real users first.<\/p>\n\n\n\n

Another way to visualize this is to look at the way many stores divide checkout lines into full service, \u201c10 items or less\u201d, and self-checkout lanes. Traffic can be divided and prioritized in ways ensuring that as many transactions as possible can be processed efficiently. In this way the traffic overburdens neither the customers nor the cashiers.<\/p>\n\n\n\n

Another dilemma other hosts present is that when a server is barraged with uncached traffic, they simply begin denying all new requests. On WP Engine our system intelligently chooses oldest waiting requests to be rejected. This allows your site to still accept new traffic in the process. That means instead of high traffic simply taking your site down, your site can still support new traffic continuously through it.
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Traffic Queueing<\/h2>\n\n\n\n

WP Engine segments traffic into several queues, the queues then have their own level of priority to feed into the PHP workers. Requests are sorted in the following order:<\/p>\n\n\n\n

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  1. Traffic is sorted by account\n