Cache & Carry
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Enabling both proxy_cache_use_stale updating and proxy_cache_background_update in Nginx can enhance performance by serving stale responses while updating the cache in the background. However, this can lead to increased response times due to request blocking in high-traffic situations with HTTP/1.1 keepalive. A workaround involves closing connections on stale and expired cache responses to mitigate delays.
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Request coalescing is an important technique in edge caching that reduces origin server load by letting one request fill the cache while others wait. Nginx implements this via the proxy_cache_lock directive, but it adds up to 500ms to response time. A proposed patch, which allows the parameter to be configured, leads to lower response times. Implementing a hit-for-pass mechanism can further enhance performance by allowing certain requests to bypass cache locking altogether.
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The guide focuses on optimising and debugging edge caching on the WordPress VIP platform. I share insights on enhancing performance for WordPress and Node.js applications, along with troubleshooting edge behaviour.