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Comment by jbergstroem | Hacker News Reader

Out of curiosity: how does people using Wordpress [at somewhat scale] handle layers of cache? Last I used it, relying on the Wordpress cache layer just didn't cover enough cases. The MySQL one "saved" me seeing how Wordpress likes to ask the same question. A lot.

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If you enable WordPress's object cache, it should get most page views down to a couple or even zero queries. It's poorly written themes and plugins where problems can arise.

The easy solution is to just enable full page caching. On single server setups, something like WP Super Cache works well. On distributed setups like WordPress.com, this is more appropriate: https://github.com/Automattic/batcache

The object cache doesn't persist across HTTP requests. You have to install some 3rd party plugin for that.[1]

[1]https://codex.wordpress.org/Class_Reference/WP_Object_Cache

Correct, which is what I meant by enabling it. Apologies for not being clearer.

It used to persistent via writing objects to the filesystem but it actually ended up being _slower_ in some configurations.

Having an object cache is one layer. However, caching SQL in conjunction could speed up application response times, depending on the behavior of the workload. I have seen the performance increase by 4x by caching SQL.

Primarily by putting a caching proxy server like Varnish in front of Wordpress.

Yep, this is what we do. Adding in some kind of object cache cluster wasn't a significant enough of an improvement over just hitting mysql to justify the extra point of failure.

The problem is WP just makes a ton of simple queries - in any complex install the bottleneck is probably going to be network latency to the database.

I think this echo's Rene's point about moving the cache closer to the application as well.

I have some hypothetical numbers illustrating the impact of network latency: http://www.tocker.ca/2013/11/18/how-important-is-it-to-merge...

The simple queries are basically free once they get to MySQL. Query cache does not help.

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