I've recently started a new application in PHP which has very strict time / performance requirements. I could build it in another language, but I'm most familiar with PHP, the thing would take me 4x as long to build in Rust.
The default frameworks (Laravel and Symfony) are very slow out of the box, and doctrine / propel are pretty slow as well.
I've instead built something entirely brand new using Swoole and an assembled set of very fast and very light Composer packages (namely Fastroute and PHP-DI) and everything else I'm building myself (compromising on reusability and full-featuredness in return for raw performance).
I've split the code in to two: one half is the framework, it's concerned with routing, dependency injection, models and hydration, event handling and responses. The other half is focussed on the business concerns: creating users, creating authentication token, performing searches.
There were a few challenges: moving from single row, single model queries to hydrating complex joined collections was a major multi-day challenge, but the end result is that when a request has all the data it needs cached, it responds in ~3ms, when it needs something from the database it responds in ~10ms.
I was apprehensive when I started, and a half decade ago this codebase would be an unmaintainable mess, but I'm finding it a joy to work in: there are few layers of abstraction, not a single line of code is wasted, and when something goes wrong there's no magic obfuscating the true problem.