Author here. You're right that if you end up dealing with many requests per second, it will end up being resource intensive. In that case, the file or even a dedicated queue are better options.

We actually queue calls to our API and send only a single request to our servers. Even if you make multiple API calls over the course of a request, there will still be one fork per request.

I'd actually wanted to include UDP, PHP Extensions, and persistent sockets as part of the article, they just ended being a little out of scope. We might try and support them in the future, UDP is definitely an interesting idea for analytics applications.

We may also end up writing a custom in-memory queue which uses a persistent socket. For a vanilla PHP install, these seemed like the best available options.