How many platforms can a programmer know?

Question

Programming

Hello everyone
I noticed that vacancies began to appear more and more often, where the employer requests knowledge of several platforms.
For example Python (Django / Celery / Django REST framework) + Java (Spring). Those. not just knowledge of the language that will theoretically be used, but a confident knowledge of frameworks and tools.
So the question is, how many platforms can you know to sit down and go?

Answer 1

One is enough.
I don't understand why you need ALL jobs? Become an expert in something, find a job for yourself and work. In parallel, you can find yourself another hobby and explore another, well, third.
But to study everything?.. You don't have a personal life or you don't want it?

Answer 2

Yes, as much as you want. Just keep in mind: while you're "studying" the third platform you don't need, your friend will make good money on a single one. Your problem is not that you do not know some platforms from the announcement, but that you do not know who and how writes such announcements.
A girl is sitting, usually a close relative of someone from the leadership. The poor thing doesn't know anything and can't do anything, but her position is called "personnel manager" (or something like that). Here she is given the task to advertise, she writes anything and more without understanding the topic. In real life, people can get all this knowledge only by the age of 40 (and then by chance) and have a salary of 5000-10000 dollars, and the vacancy requires an age of no older than 30 and involves a payment of no more than $500. does not know the platform

Answer 3

In general, I often see people who know the three platforms pretty well.