The two fundamental ways encryption algorithms process data.

The two notification modes for I/O multiplexing, why edge-triggered is trickier, and when each one matters.

Both let processes talk to each other, but the abstraction level changes everything about how you use them.

How to tell where one message ends and another begins, and why getting it wrong opens you up to buffer overflow and DoS attacks.

I don't like Java, I love Zig and Rust, and neither of those feelings matter when network latency is 10,000x bigger than your FFI overhead. A case study in not rewriting things.

The two places your data lives, how they differ, and the use-after-free bug that taught me why it matters.

How I learned that Zig's HashMap stores pointers, not data, and why that creates use-after-free bugs if you're not careful.

The two string types in Rust, when to use each, and why the distinction actually matters for memory management.