Overall response should be under 10 minutes. If you're getting tons of followup questions, that means that you're winging it and are underprepared. Preliminary Define Scope: Target audience, accepted payment, geographic limits, performance SLAs, browser support, etc List your assumptions: Limit the supported browsers, payment types, geography, languages, etc Tests Functional Positive: A nice list of UI, apis, backend persistence, state caching, etc testcases Functional Negative: A few examples conveying your understanding of limitations Performance: Like the previous example, multi-threading, Security: SQL injection attacks, XSS, url manipulation, Cross-browser/platform support (usability): test on many platforms, focus on IE support if applicable Localization (usability): CMS translation files are loaded and rendered properly Accessibility (usability): Proper element tagging (e.g. aria labels), voiceover tools, page element tab order Conclusion Ask interviewer if there is anything that you need to expand on