What is an ETag and how does it help with caching?

Updated Apr 28, 2026

Short answer

A unique identifier for a version of a resource; helps the client check if their cached copy is still valid without a full download.

Deep explanation

Intermediate caching involves choosing strategies that balance speed with data accuracy. A unique identifier for a version of a resource; helps the client check if their cached copy is still valid without a full download.

Real-world example

Using Redis to store session data across a cluster of web servers.

Common mistakes

  • Using Write-Back caching for critical financial data without a robust safety net for data loss.

Follow-up questions

  • What is a 304 HTTP code?

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