Varnish Cache: Performance Turbo for Drupal Platforms

Varnish is an HTTP accelerator that sits as a reverse proxy in front of the web server. When a visitor requests a page, Varnish first checks its cache. If the page is available, it is delivered directly from memory — in microseconds.

Only when the page is not in the cache or has expired does Varnish forward the request to Drupal. The result is cached and kept ready for subsequent requests.

Drupal comes with a mature cache system that works perfectly with Varnish. The core components:

Cache tags. Drupal marks each page with tags indicating which content is included. When content changes, only the affected pages are invalidated.

Purge module. The Purge module sends invalidation requests to Varnish when editors change content. Outdated pages are selectively removed — not the entire cache.

Cache-Control headers. Drupal sets cache headers by default that control Varnish. The maximum cache duration is configured in the performance settings.

Without Varnish, Drupal recalculates every page on every request. For complex pages with Views, taxonomies, and references, this takes 200-500 milliseconds. With Varnish, the response time is 1-5 milliseconds.

For platforms with high traffic — publishing portals, corporate websites with thousands of page views per minute — Varnish is not a luxury but a necessity.

arocom configures Varnish as part of the hosting architecture. The Future Check identifies performance bottlenecks and recommends concrete measures. From 2,500 EUR plus VAT, creditable toward the follow-up project.