Sweaty Imposter

Low-Level Design Round

Design the classes, an API, or a schema for a small product in about 45 minutes. It shows up most at Mid and Senior, often in place of a second coding round.

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Length
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Set a level to tune the cards. Cards you rated Shaky come up more often.

How It's Graded

  • Junior

    Sensible classes with clear names, and code that compiles in your head.

  • Mid

    Clean responsibilities, one or two patterns used for a reason, and an API that fits the use cases.

  • Senior

    Extension points where change is likely, concurrency handled, and the schema and indexes to match.

  • Staff

    The same design defended under new requirements, with a plan to evolve it without breaking callers.

  • Principal

    Seldom asked. When it is, expect questions on API contracts across teams and versioning.

Drill Types

Read These First

All Object Design Prompts

Common Mistakes

  1. Starting with inheritance

    Find the nouns and their jobs first. Most hierarchies get flatter once you do.

  2. Patterns for their own sake

    Use a pattern when it solves a change you can name.

  3. Forgetting concurrency

    Two people booking the last spot is usually the follow-up question.

Matching Mock

Mixed Timed Drill

A timed set of cards from several rounds, with a report at the end.

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