It would be useful if ksqlDB had a NULLIF function, as common across SQL in other platforms.

Example from postgres:

NULLIF(value1, value2)
The NULLIF function returns NULL if and only if value1 and value2 are equal. Otherwise it returns value1.

Currently, you are not able to use middleware per handler in "clean way" (you can still manually wrap the handler function, or have separated router).

It would be nice to be able to add middleware per handler.

As a good reference point, you can use chi router: https://github.com/go-chi/chi

我看到可以通过Prometheus搭建监控环境，如果有图文，更容易理解．