Browser APIs and Web Platform Questions

Practical knowledge of core browser platform features and their performance, security, and reliability trade offs. Topics include the Document Object Model for traversal and manipulation, event handling and delegation, storage APIs such as local storage and IndexedDB, the Fetch API and XMLHttpRequest, IntersectionObserver and ResizeObserver for efficient rendering, Web Workers and service workers for background tasks, and considerations around serialization, thread boundaries, and resource limits. Candidates should also be able to measure and debug platform interactions and reason about when to use a particular web platform primitive.