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Paul Calvano’s Blog
Site URL: paulcalvano.com
Feed URL: paulcalvano.com/feed.xml
Posts: 10
Followers: 1
Investigating a Curious Case of Font Format Fallbacks
https://paulcalvano.com/2026-10-18-investigating-a-curious-case-of-font-format-fallbacks/
Published: October 19, 2026 10:09
Every month the NY WebPerf Meetup runs a session called Meet4Speed, where Sergey Chernyshev and I meet with members of the local developer community and talk about web performance. It’s an incredibly fun and interactive meetup. There is no presenter in…
Resource Age and Its Impact on Cacheability
https://paulcalvano.com/2026-09-05-resource-age-and-its-impact-on-cacheability/
Published: September 5, 2026 15:01
When deciding how long to cache a response, it’s important to consider how often the response may change as well as the cost of revalidation. A resource that is updated frequently would benefit from a short cache duration, which offloads the origin while…
Serving Static Content with Cloud Storage? Don’t Forget the CDN!
https://paulcalvano.com/2026-02-09-serving-static-content-with-cloud-storage-dont-forget-the-cdn/
Published: February 9, 2026 12:26
Many websites use cloud storage as part of how they deliver static content to end users. However using these services without a CDN in front of them has the potential to negatively impact performance. You might be surprised by how many sites do just that -…
Third Parties and Single Points of Failure
https://paulcalvano.com/2025-12-29-third-parties-and-single-points-of-failure/
Published: February 7, 2026 18:51
You’ve heard it many times - third party content can easily cause an otherwise well performing website to become sluggish and slow. And depending on how this content is loaded, it can also introduce single points of failure (SPOFs). When a large cloud…
AI Bots and Robots.txt
https://paulcalvano.com/2025-08-21-ai-bots-and-robots-txt/
Published: September 1, 2025 15:16
There’s been a lot of discussion lately around AI crawlers and bots, which are used to train LLMs and/or fetch content on behalf of their users. In the past few weeks I’ve seen blog posts about the amount of traffic from these crawlers, techniques and…
Discovering Third Party Performance Risks
https://paulcalvano.com/2024-09-03-discovering-third-party-performance-risks/
Published: September 4, 2024 11:06
It likely comes as no surprise that third party content can be a significant contributor to slow loading websites and poor user experience. As performance engineers, we often need to find ways to balance requirements for their features with the strain that…
Third Parties and Certificate Revocations
https://paulcalvano.com/2024-08-04-third-parties-and-certificate-revocations/
Published: August 5, 2024 03:12
On Monday July 29th, DigiCert announced the need to revoke a large number of certificates due to a bug in domain validation. The CA/B Forum’s strict requirements to revoke these certificates within 24 hours resulted in a pretty busy Monday and Tuesday for…
Choosing Between gzip, Brotli and zStandard Compression
https://paulcalvano.com/2024-03-19-choosing-between-gzip-brotli-and-zstandard-compression/
Published: March 19, 2024 14:18
HTTP compression is a mechanism that allows a web server to deliver text based content using less bytes, and it’s been supported on the web for a very long time. In fact the first web browser to support gzip compression was NCSA Mosaic v2.1 way back in…
Identifying Font Subsetting Opportunities with Web Font Analyzer
https://paulcalvano.com/2024-02-16-identifying-font-subsetting-opportunities/
Published: February 17, 2024 19:20
10 years ago, custom web fonts were a niche feature used by ~10% of websites. Today they are used by over 83% of websites! Fonts are generally loaded as a high priority resource, and some sites use techniques such as preload and early hints to get them to…
Internet Explorer’s Decline in Usage in 2021
https://paulcalvano.com/2022-01-31-internet-explorer-decline-in-2021/
Published: January 31, 2022 17:50
In May 2021 Microsoft announced that it would be officially retiring Internet Explorer in favor of the Chromium based Microsoft Edge. Usage for the legacy browser had been very low over the past few years, although many websites have still maintained…