Web performance consultant for Fastly
Program performance with Fastly
Fastly is the most programmable CDN on the market. Custom VCL, sub-second instant purge, Compute@Edge: I program the edge layer to deliver real-time TTFB and stable Core Web Vitals, even on e-commerce or media sites with heavy personalization.
They trust me
Symptoms justifying a Fastly audit
Fastly's power sits in VCL programmability. Poorly written, VCL costs without delivering. Well-written, it delivers experiences other CDNs can't match.
📝 Legacy VCL, unreadable, no longer optimizing anything
Varnish Configuration Language governs every cache, header, vary decision. Well-written VCL doubles the hit ratio and stabilizes TTFB. VCL piled up over five years becomes dead weight.
⏱️ Purging via short TTLs instead of instantly
Fastly Instant Purge invalidates globally in under 150ms. It enables long-term caching (24h+) with surgical invalidation at deployment. Perceived TTFB collapses, Core Web Vitals stabilize.
🚀 Compute@Edge unused for personalization
WebAssembly at the edge, sub-millisecond execution, compiled languages (Rust, Go, JS/TS). Personalization without paying the origin round-trip. Ideal for A/B, geo, auth, image proxying.
🖼️ Fastly Image Optimizer disabled or misconfigured
Auto format, responsive resizing, per-device sizing: Fastly Image Optimizer generates the right asset per request. Paired with clean VCL, image LCP gains 200 to 500ms.
🔑 Surrogate-Key strategy missing or disorganized
Without a coherent Surrogate-Key naming, you're forced into short TTLs to stay fresh. With one, you cache 24h+ and purge surgically at deployment. Perceived TTFB drops.
📡 Real-Time Log Streaming unused
Fastly streams its logs in real time to your tools (Datadog, S3, Sumo). Performance debugging in live, cache-level A/B testing becomes possible, fine analysis of edge behavior opens optimizations invisible otherwise.
Fastly optimization methodology
4 steps to transform your performance
1. Existing VCL audit
Read custom VCL with a performance lens: cache rules, header handling, Vary, purge strategy. Identify obsolete or counter-productive rules.
2. Surrogate-Key strategy
Define a coherent Surrogate-Key naming (per section, product, taxonomy). Enables long-term caching and instant invalidation at the right granularity.
3. Image Optimizer + critical path
Activate and calibrate Image Optimizer (auto format, sizing). Prioritize LCP image via fetchpriority and edge preload.
4. Compute@Edge where relevant
Identify edge use cases winning performance (A/B, auth, geo, image proxying). Rust or JavaScript implementation with monitoring via Real-Time Log Streaming.
1. Existing VCL audit
Read custom VCL with a performance lens: cache rules, header handling, Vary, purge strategy. Identify obsolete or counter-productive rules.
2. Surrogate-Key strategy
Define a coherent Surrogate-Key naming (per section, product, taxonomy). Enables long-term caching and instant invalidation at the right granularity.
3. Image Optimizer + critical path
Activate and calibrate Image Optimizer (auto format, sizing). Prioritize LCP image via fetchpriority and edge preload.
4. Compute@Edge where relevant
Identify edge use cases winning performance (A/B, auth, geo, image proxying). Rust or JavaScript implementation with monitoring via Real-Time Log Streaming.
Mission commitments
Frequently asked questions
Does Fastly improve web performance?
Do you need to know Varnish to use Fastly?
Fastly Instant Purge: why is it a performance lever?
Fastly vs Cloudflare vs Akamai for performance?
Pull maximum performance out of Fastly
Data 2023-2026
What my clients say
Excellent work.
Paul has significantly improved the site's speed and perfectly aligned it with Google's recommendations.
Professional, thorough, and efficient, I highly recommend.
Nicolas - April Moto
Digital & E-commerce Director
We are very satisfied with Paul's work. He is quick, available, and particularly effective. Since his arrival, very good results have been observed, both in terms of performance and responsiveness. A real asset for our team.
Léo - Luxury brand
E-commerce Product Owner
I don't know if we've said it enough.
But if you want to improve your loading speed,
Make Google happy and get your Core Web Vitals in the green,
Contact Paul Delcloy.
Florian Darroman - Les Makers
Co-founder
Fastly, the programmable CDN for demanding sites
Fastly is less plug-and-play than Cloudflare for the general public, but its power outshines competitors when you need to program the edge layer. It's the historical CDN of publishers (New York Times, GitHub, Stripe), premium e-commerce (Shopify) and any infrastructure where cache freshness, edge personalization and fine-grained network control are critical.
Fastly's strength sits in custom VCL (Varnish Configuration Language), sub-second instant purge, and Compute@Edge (WebAssembly). Poorly used, Fastly costs a fortune for a result no better than any other CDN. Well-used, it delivers experiences others can't match: long-term caching with surgical invalidation, personalization without origin round-trip, sub-millisecond edge decisions.
VCL, the Fastly performance nerve center
On a Fastly mission, VCL is the first place I look. Varnish Configuration Language governs every decision on cache, header, Vary, purge strategy. Well-written VCL doubles the hit ratio and stabilizes TTFB. VCL piled up over five years becomes unreadable, contradictory, expensive.
The VCL audit reads each rule with a performance lens: obsolete rules to remove, contradictory behaviors to arbitrate, simplification opportunities, cache keys to recalibrate. Results show immediately: fewer origin misses, perceived TTFB dropping, Fastly bill shrinking.
Instant Purge + Surrogate-Key for long-term caching
Fastly's sub-second instant purge is its most differentiating lever. Paired with a well-defined Surrogate-Key strategy (per section, per product, per taxonomy), it allows 24h+ caching while keeping freshness at every deployment. No more short TTLs to force freshness: long cache + surgical purge at the right granularity.
The gain shows on TTFB (cache hit ratio climbing to 95%+) and on Core Web Vitals stability. Fewer incidents during traffic peaks, no more cache stampedes on mass invalidations. For a complete CDN strategy rollout, the Fastly intervention often combines with a broader web performance audit.
Other expertise CDNs
Angular
Angular optimized: lazy modules, OnPush change detection, SSR Universal or Analog, signals, zone.js elimination. Stable Core Web Vitals on enterprise SPAs.
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Astro
Astro optimized: islands architecture, image optimization, view transitions, content collections. Near-static sites with green Core Web Vitals.
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Drupal
Drupal optimized: Render API and cache contexts, Dynamic Page Cache + BigPipe, Views performance, MySQL tuning. Core Web Vitals green on strategic templates.
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