Technology-agnostic fundamentals that underpin every system design. These are the building blocks: how networks behave, how to model data, how to design APIs. Patterns build on these; without them, pattern-level answers lack grounding (see Patterns Taxonomy).
🔴 P0 — the first design decision that cascades into everything else: scaling, consistency, query performance
🔴 P0 — the craft of designing APIs; shows engineering judgement, not just pattern knowledge
🔴 P0 — foundation for reasoning about inter-service communication, latency, and failure modes