# A Practice Plan and Problem List — High-Level & Low-Level Design Interview Problems

Source: https://www.skillbyai.com/en/design-interviews/practice-plan

> Deliberate, timed repetitions.

## How to practise effectively

Practise out loud and timed, as in the real round. Alternate HLD and LLD problems so both stay fresh. For each problem: attempt it in 45 minutes, then compare against a reference design or a peer review, write down the gaps (missed requirement, weak data model, no failure handling), and redo the same problem a week later. Mock interviews with a partner are the closest substitute for the real thing, because they train you to handle interruptions and hints. For LLD, actually write and run the code in your own time so you are fluent in your interview language's collections and concurrency utilities.

## A four-week plan

Adapt to your timeline and target companies.

```text
Week 1  basics: approach, estimation refresh, SOLID + 4 patterns
        LLD: parking lot, vending machine     HLD: URL shortener, rate limiter
Week 2  LLD: elevator, LRU cache, seat booking
        HLD: ride-hailing, checkout + inventory, autocomplete
Week 3  LLD: library system, logger, splitwise-style expense sharing
        HLD: video streaming, key-value store, payment ledger
Week 4  HLD: collaborative editor, job scheduler, metrics pipeline
        2+ full mock interviews (one HLD, one LLD); redo weakest two problems

After each attempt: list 3 gaps -> fix -> re-attempt in 7 days
```

## Keep a mistakes log

A short log of recurring gaps (forgot idempotency, no capacity numbers, god class) shows you what to fix and is a quick review the night before.

**Quiz:** What is the most realistic way to practise design rounds?

- [ ] Memorising one diagram per problem
- [ ] Reading many solutions without attempting them
- [x] Timed mock interviews out loud with someone giving feedback
- [ ] Practising only the problems you already know

*Answer:* Timed mock interviews out loud with someone giving feedback. Simulate the real conditions.