S: one responsibility per class (one reason to change); O: extend behavior without modifying existing code; L: subtypes must keep the contract of the base type; I: prefer small, focused interfaces; D: depend on abstractions, not concrete implementations (DI).
Advanced answer
Deep dive
Expanding on the short answer — what usually matters in practice:
Context (tags): solid, design-principles, oop
Scaling: what scales horizontally vs vertically, where bottlenecks appear.
Explain the "why", not just the "what" (intuition + consequences).
Trade-offs: what you gain/lose (time, memory, complexity, risk).
Edge cases: empty inputs, large inputs, invalid inputs, concurrency.
Examples
A tiny example (an explanation template):
// Example: discuss trade-offs for "explain-solid-in-one-sentence-per-letter."
function explain() {
// Start from the core idea:
// S: one responsibility per class (one reason to change); O: extend behavior without modifyi
}
Common pitfalls
Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).