What theoretical knowledge should an ideal back-end developer have?

Question

IT education

Hello everyone,
I would like to hear the opinion of professionals on this issue - what knowledge should an ideal back-end developer have? For example, knowledge of algorithms and structures, the algorithm of the processor and memory, etc. will not interfere with a "system" developer. A Data Scientist needs to understand mathematics and think analytically. The list can be continued indefinitely. But what should a server-side application developer know? I don't mean what languages ​​or frameworks, but theoretical knowledge that will help him develop high-end software. If it's hard to decide - write the most important 3 points, according to your opinion.
Thanks in advance for the info :)

Answer 1

The ideal, by definition, is unattainable, and therefore the upper limit of the necessary knowledge cannot be determined. At a minimum, to develop high-end software, a web developer needs to have a good understanding of networks. Yes, and knowledge of hardware and algorithms is also not at all superfluous.

Answer 2

Formal logic, basics of algorithm complexity theory, distributed systems, basics of cryptography and security.