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Front End System Design Interview - Applications

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Front End Interview Handbook is part of GreatFrontEnd! Find the latest version of this page on GreatFrontEnd.



  1. Requirements exploration
  2. Architecture
  3. Data model
  4. Interface definition (API)
  5. Optimizations and deep dive
    • User experience (UX)
    • Performance
    • Accessibility (a11y)
    • Internationalization (i18n)
    • Multi-device support
    • Security

Requirements exploration

Every system design interview should start with clarifying requirements about the question, which is usually left vague intentionally. Some considerations:

  • What devices should the system support? Desktop web, mobile web, etc
  • What's the primary device that users will access the system on?
  • Which browsers should we support?
  • Do we need to support internationalization?
  • Does the app need to work offline?

Architecture / High-level design

Architecture for front end interviews are typically focused on the client-side architecture, and not on large scale distributed systems where databases, load balancers and servers are involved.

For applications, common architectures include Model-View-Controller, Model-View-ViewModel, Flux, N-tier (where data tier is on the client) etc.

Data model

Client app state, which is a combination of server state (database) and true client state (non-persisted to the server).

Interface definition (API)

API design for applications will refer to the HTTP/network API parameters and the shape of the responses.

Optimization and deep dives

With the architectural basics of the application covered, we can dive into specific areas which the application might need special attention to. Note that there almost definitely won't be enough time to cover every area, and not every area will be very relevant to the component at hand.

Showing knowledge about these areas and being able to dive deep into them are traits of senior developers.

  • User experience (UX)
  • Performance
  • Accessibility (a11y)
  • Internationalization (i18n)
  • Multi-device support
  • Security

Helpful articles

Many companies blog about their technical challenges in the front end domain and these are great content to learn more about designing front end systems.

GreatFrontEnd shows you how to approach front end system design interviews with their front end system design guide and case studies. You can also do hands-on practice through their huge question bank, each with solutions written by ex-FAANG senior engineers to learn more about system design.