Learn Hardcore Russian: Стоит только режиссёру прийти, как съёмочная группа начинает работать. - One only has to have the director arrive, and the film crew starts working.

So in this sentence, Стоит только режиссёру прийти, как съёмочная группа начинает работать means that the crew starts working immediately once the director arrives.

A very literal breakdown would be:

стоит только = it only takes / one has only to
как = and then / when immediately after that

This structure often suggests a quick, automatic consequence.

Why is режиссёру in the dative case?

Because in this construction, the person connected with the infinitive often appears in the dative.

Here:

режиссёр = director
режиссёру = to the director / for the director

So режиссёру прийти literally feels like for the director to arrive.

This is a common Russian pattern with infinitives, especially when Russian expresses something like:

someone to do something
for someone to do something

Compare:

Мне уйти? = Should I leave? / Am I to leave?
Ему трудно понять это. = It is hard for him to understand this.
Стоит только режиссёру прийти... = As soon as the director arrives...

Why is the verb прийти in the infinitive instead of a finite form like придёт?