# A Compact Approach for Each Round — High-Level & Low-Level Design Interview Problems

Source: https://www.skillbyai.com/en/design-interviews/round-approach

> Requirements, entities and APIs, design, trade-offs.

## Four steps that work for both

Use the same skeleton for both rounds. (1) **Requirements**: clarify functional scope and non-functional goals (scale, latency, consistency); write them down. (2) **Entities and APIs**: for HLD, list core data entities and the main API calls; for LLD, list classes and their key methods. (3) **Design**: for HLD, draw the request path and data stores, then deep-dive into the hardest part; for LLD, define interfaces and relationships, then implement the core flow. (4) **Trade-offs**: explain alternatives you rejected, bottlenecks and failure modes. The System Design Interview Prep course covers estimation and building blocks in depth; here we apply them.

## A time budget for a 45-minute round

Adjust to the interviewer; these are guidelines, not rules.

```text
HLD (45 min)                         LLD (45 min)
 0-5   requirements + scale           0-5   requirements + use cases
 5-10  entities, APIs, estimates      5-12  classes, relationships
10-25  high-level diagram            12-35  interfaces + core code
25-40  deep dive (1-2 components)    35-42  edge cases, concurrency
40-45  trade-offs, failures          42-45  extensions, trade-offs
```

## Say the plan out loud

Telling the interviewer your plan in one sentence lets them redirect you early, which saves far more time than it costs.

**Quiz:** What should come first in either round?

- [x] Clarifying requirements and scope
- [ ] Writing the database schema
- [ ] Picking a message broker
- [ ] Implementing the hardest method

*Answer:* Clarifying requirements and scope. Design follows requirements.