Vertx on the other hand, which it is built on and which itself builds on Netty, is excellent, and very performant for typical backend services. It now has support for virtual threads too.
Quarkus is just compile time stuff around vertx, and you write simple synchronous code. Again, DO NOT use vertx directly for building APIs. It'd be like using just expressjs and writing your api specs manually... in 2025...
Deviating from Quarkus's standard behaviour was comparatively difficult, either tracking down the correct configuration properties and what to change them to, or which api to implement and override and what it needs to do.
I prefer to develop OpenAPI specs separately from the code too, mainly because it's a joint effort with other teams. Vertx can incorporate them easily.
My advice: If you are just building a regular service that doesn't need to scale (and 90% of apps do not need Twitter scale), just stick with sync.
What does the highlighted part above mean?
I know what Netty is, but did not understand that phrase above,