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Performance Blog

Insights, tips, and deep dives into web performance optimization. This page demonstrates CSS @import flattening and script combining.

Optimization Features on This Page

  • flatten_css_imports — 3 CSS files loaded via @import are inlined
  • combine_css — remaining link tags are combined into fewer requests
  • combine_javascript — 3 script tags are merged into one request
  • rewrite_css / rewrite_javascript — CSS and JS are minified
  • collapse_whitespace — excess HTML whitespace is removed
  • remove_comments — HTML comments are stripped
  • rewrite_style_attributes — inline style attributes are minified
Server infrastructure Infrastructure

Understanding Server Response Times: A Deep Dive into TTFB

March 15, 2026 · 8 min read · By Alex Thompson

Time to First Byte (TTFB) is often the most overlooked metric in web performance optimization. While much attention is given to client-side rendering and asset optimization, the server response time sets the fundamental baseline for how quickly a page can possibly load.

In our experience working with enterprise clients, we've found that TTFB improvements of just 100-200ms can cascade into significantly better user experience metrics across the board. The reason is simple: every millisecond saved on the server is a millisecond saved for every single user, on every single page load.

"The fastest request is the one that never has to be made. But for the requests that must happen, the server's response time is the non-negotiable starting point of the user's experience."

Key strategies for reducing TTFB include: implementing server-side caching with appropriate invalidation strategies, optimizing database queries with proper indexing and connection pooling, using reverse proxy caching (like Varnish or nginx microcaching), and choosing hosting infrastructure that minimizes network latency to your target audience.

Modern CDN providers also offer edge computing capabilities that can reduce TTFB by executing server logic closer to the user. However, this approach requires careful consideration of cache coherency and data freshness requirements.

Development workspace Performance

The Hidden Cost of Render-Blocking Resources

March 10, 2026 · 12 min read · By Sarah Chen

One of the most common performance anti-patterns we encounter in production websites is the excessive use of render-blocking CSS and JavaScript. Every external stylesheet linked in the <head> of your document blocks the browser from rendering any content until the CSS is downloaded and parsed.

Quick Optimization Tips

  • Use media attributes to load print/mobile CSS conditionally
  • Inline critical CSS directly in the <head>
  • Defer non-critical JavaScript with async or defer
  • Split CSS bundles by route for single-page applications
  • Use preload hints for fonts and critical resources

The solution is not simply to move everything to async loading — that can cause flash-of-unstyled-content (FOUC) issues. Instead, the recommended approach is to identify the critical CSS needed for above-the-fold content and inline it directly, while deferring the rest. Tools like mod_pagespeed can automate this process by analyzing which CSS rules are actually needed for the initial viewport.

For JavaScript, the defer attribute is generally preferred over async because it maintains execution order while still allowing the browser to continue parsing HTML. Scripts that modify the DOM should use defer, while truly independent scripts (like analytics) can use async safely.

Our analysis of 500+ production websites shows that the average site loads 14 external CSS files and 23 JavaScript files. By combining and inlining appropriately, most sites can reduce their render-blocking resources to just 1-2 requests, saving 500ms-2s on typical 4G connections.

Team discussion Strategy

Image Optimization in 2026: Beyond Simple Compression

March 5, 2026 · 15 min read · By Marcus Rivera

Images typically account for 50-70% of a web page's total transfer size. While basic compression has been standard practice for years, modern image optimization involves a sophisticated pipeline of format selection, quality tuning, responsive sizing, and delivery optimization.

The landscape of image formats has evolved significantly. WebP offers 25-35% better compression than JPEG for equivalent quality, while AVIF pushes this further with 50% improvements in many cases. However, format support varies across browsers, making content negotiation essential.

Server-side image optimization modules like mod_pagespeed handle this complexity automatically. When a request arrives, the module checks the browser's Accept header, selects the optimal format, applies quality-aware compression, and caches the result for subsequent requests. This eliminates the need for build-time image pipelines and ensures every visitor gets the best possible format.

Beyond format conversion, modern optimization includes:

  • Responsive images: Serving appropriately sized images based on the viewer's viewport and device pixel ratio
  • Lazy loading: Deferring below-the-fold image loads until the user scrolls near them
  • Progressive rendering: Converting to progressive JPEG so images render incrementally
  • Metadata stripping: Removing EXIF data, ICC profiles, and other metadata that users don't need
  • Content-aware quality: Applying higher compression to regions of the image with less visual detail

The combined effect of these techniques typically reduces image transfer size by 60-85% without any visible quality degradation. For an average web page with 2-3 MB of images, this translates to 1-2 seconds of saved load time on mobile networks.