Frontend System Design
/Advanced
ETag & Cache Validation
Definition
An ETag (Entity Tag) is an HTTP header containing a unique hash of a file's contents. When a cached file expires, the browser sends the ETag back to the server (`If-None-Match`). If the file hasn't changed, the server returns a 304 Not Modified, saving massive bandwidth.
Explain Like I'm New
The browser asks: 'Hey, I have a file with the fingerprint 12345. Is it still the newest version?' The server says: 'Yes, don't redownload it.'
Architecture & Flow
Interview Questions
basic
- How does ETag fundamentally work?
intermediate
- What are the performance implications of ETag?
advanced
- How does ETag scale in an enterprise architecture?
trick
- Are there scenarios where ETag is an anti-pattern?