Learning Path
Improve HTTP Performance and Caching
A practical path for faster responses, safer caching, and better client-server efficiency.
Built for: Engineers working on API latency, browser performance, CDN behavior, and cache correctness.
What you should get from this path
- Choose sane Cache-Control policies.
- Understand validators, freshness, and conditional requests.
- Spot performance headers that matter for browsers and caches.
Read the performance guides
These pages provide the higher-level model for cache behavior and protocol performance.
- Guide
HTTP Headers and Caching: A Practical Guide
Master HTTP caching with Cache-Control, ETag, Last-Modified, and conditional request headers. Learn how to optimize performance with proper cache strategies.
Explains how headers combine to control browser and intermediary behavior.
- Guide
HTTPS Explained: How TLS Secures HTTP
HTTPS is HTTP over TLS. What the TLS handshake does, how certificates prove identity, what HTTPS hides and what it does not, and how to migrate a site safely.
Covers the transport overhead and security foundation underneath HTTP performance.
Know the headers that matter
Use these references to move from general theory to exact directives.
- Header
Cache-Control Header: Directives, Examples and CDN Behavior
Cache-Control directives explained: max-age, no-cache vs no-store, s-maxage, stale-while-revalidate, immutable, with nginx, Cloudflare and Next.js examples.
Primary control surface for freshness, revalidation, and cacheability.
- Header
ETag Header: Strong vs Weak, If-None-Match and 304 Debugging
ETag identifies a resource version for cache validation and optimistic locking. Strong vs weak ETags, If-None-Match, If-Match, and why nginx gzip weakens them.
Needed for conditional requests and avoiding unnecessary payload transfers.
- Header
Last-Modified
Learn how the Last-Modified header indicates when a resource was last changed. Enable efficient cache validation with If-Modified-Since conditional requests.
A simpler validator that still matters for many browser and CDN flows.
- Header
Vary Header: Cache Keys, Vary: Origin and Accept-Encoding
Vary lists the request headers a response depends on, so caches keep separate copies. Vary: Accept-Encoding, Vary: Origin for CORS, Vary: *, and CDN cache keys.
Essential when cache behavior differs by language, encoding, or other request traits.
- Header
Server-Timing Header
Learn how the Server-Timing header communicates server-side performance metrics to browsers. Analyze backend timing, database queries, and optimize performance.
Useful for exposing backend timing data during performance analysis.
Use tools and comparisons
These help turn policy decisions into concrete checks and tradeoff analysis.
- Tool
Cache-Control Builder
Compose caching directives and get plain-English explanations instantly.
Quickly sanity-check combinations like public/private, max-age, and stale directives.
- Tool
Header Inspector
Inspect real-world responses for cache headers and related response metadata.
Lets you confirm that intended policy matches actual server output.
- Comparison
304 Not Modified vs 200 OK
Compare cache revalidation responses against full successful responses.
Explains the practical difference between revalidation and a full successful response.
- Comparison
HTTP/1.1 vs HTTP/2
Understand the protocol and performance tradeoffs between HTTP versions.
Useful when performance questions extend beyond caching into connection behavior.
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