php offers an extension called Semaphore, Shared Memory, and IPC. It uses UNIX (and Linux and BSD) features that have been around for over a quarter century and work well.

I wonder if it would be possible to use that extension to build a persistent object cache for WordPress?

An object cache can get rid of SQL bottlenecks, and so improve end-user response time and save data center power. Those things save carbon emissions.

There are some obvious disadvantages of shared memory compared to using redis or memcached, like limited segment size.

But there’s a big advantage: sites on (some) budget hosts could use it even without having access to redis or memcached. And, there are many sites on budget hosts.

Has anybody done this? Tried to and failed? Any big pitfalls?