Ask HN: Language-agnostic concepts a Backend Engineer should know?

C and how to debug it.

If you understand the system a layer of abstraction or two below the layer you work in, you will be able to debug deeper. Learn system calls, Various ways how to examine processes.

I learnt a lot of this back in the day by completing war games on a site called digital evolution (dievo). Those are antiquated now but still a really fun way to learn it.

Security mindset: read the book Security Engineering (it is online), less for specific technical info than for the many war stories etc. which will help you guard against vulnerabilities and unforeseen consequences.

Basics of cryptography: there are many dumb errors to avoid.

Antirez's general advice about "10x programmers" is good: http://antirez.com/news/112

Thorough (not just basic) knowledge of SQL, if you don't count that as a language. The sqlite.org "technical and design documents" about sqlite's virtual machine and its query planner are well worth reading, and apply to other databases as well. ORM's are less important than SQL, and are usually language specific as someone mentioned.

Reasonable clue about socket programming, even if you're doing everything with libraries that wrap the details.

Comfort using debugging and profiling tools.

Lots of other stuff, I'm sure.

I think it's important to know about different data storage options and their trade-offs. Managing state is one of the hardest parts of backend development, particularly at scale, so an understanding of the trade-offs in databases/caches/blob-storage/queues, and when each is useful is important.

I'd pay close attention to speed and "correctness". What's the consistency model of a system? Can we lose data and if so how? What's the throughput? Latency?

These help choose good technology for backend systems, and helps answer questions like:

- Can we do this in-band while serving a user request?

- Can we do it 100 times to serve a request?

- If it completes successfully can we trust it or do we still need to handle failure?

- Can we trust it immediately or eventually?

There are lots of technologies and terms for all of this but I've specifically avoided them because the important bit is the mental model of how these things fit together and the things they allow/prevent.

Slightly related, what are the most high-quality resources for learning backend engineering?

Having a good knowledge of HTTP is useful in many different contexts.

- The correct semantics for each HTTP method

- What different status codes indicate

- Common headers, particularly around caching

- HTTP 1.1 vs HTTP 2

- Common authentication protocols - OAuth 2.0, JWTs, etc.