Design a component library
hardComplete guide with examples and interview questions · 45 min
Say it out loud in an interview — clear, simple, no textbook wording.
If someone asks me to design a component library, I would say it is a versioned package of primitives built on design tokens, where teams get consistency by default and customization through composition. It is not a folder of shared components. The difference is the contract: versioning, documentation, and a migration path when the contract changes.
Interviewers care because a library is a product with internal customers. The design questions are about governance as much as code. Who decides what enters the library, how breaking changes ship, and what happens when a team needs something the library does not offer.
The senior nuance is restraint again. A library that accepts every request becomes a pile of one-off components with a shared name. The strongest libraries say no often, and give teams a clean escape hatch for the rest.
Key takeaways
- •A component library is a versioned contract, not a folder of shared components
- •Design tokens are the theming API: color, spacing, and type flow from tokens, not hex codes
- •Composition beats configuration: small primitives combine, mega-props do not scale
- •Breaking changes need a migration path, or teams will pin the old version forever
- •Accessibility is a shipped feature of each component, not a later audit
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