Native Ghost Image Optimization vs External CDN: Which Reduces Mobile Bandwidth More Effectively?

Goal

Determine which image delivery strategy better preserves page load speed on a 3 Mbps mobile connection while keeping Ghost’s CPU usage and image quality consistent.

Constraints & Uncertainty

Ghost’s built‑in Sharp pipeline resizes and compresses on‑the‑fly, but the quality setting in config.production.json is not applied to cached images unless the /content/images/size folder is cleared. An external CDN can offload resizing to the edge and automatically serve WebP/AVIF, but introduces DNS lookup latency and may deliver stale images if pull rules are misconfigured. The trade‑off between reduced origin CPU load and potential cache‑miss latency is unclear under tight bandwidth limits.

Questions

• Does the native pipeline honor the quality setting on repeated requests after the cache is cleared, and how does that affect mobile data usage?
• What is the first‑byte latency difference when Ghost serves a resized image natively versus when the request is redirected to a CDN endpoint on a 3 Mbps connection?
• Should the CDN be configured to serve WebP/AVIF only for browsers that support them to avoid fallback overhead on mobile devices?