Fastly CDN causing slow loading of assets from SteamPowered, Gog, and Vimeo

I’m seeing many requests for assets from a number of Fastly customers such as SteamPowered, Gog, and Vimeo take multiple seconds to load even very small (2-3 KB) assets (images, css, js, etc.). This only happens via my home ISP (GiggleFiber), but if I use a VPN, while overall transfer rates are of course slower, the response time for each request is more normal (a few hundred milliseconds).

Some random examples (all from Firefox’s network inspector):

URL: GET hxxps://shared.fastly.steamstatic.com/store_item_assets/steam/apps/2246340/970508d58e4f11f6f9ff3e2921b7eec558a50af8/capsule_184x69.jpg?t=1730880879
Transferred: 7.37kB
x-served-by: cache-dfw-kdfw8210084-DFW
timings:
Blocked: 60 ms
DNS Resolution: 0 ms
Connecting: 0 ms
TLS Setup: 0 ms
Sending: 0 ms
Waiting: 602 ms
Receiving: 6.12 s
(At some times, SteamPowered seems to use CloudFlare instead of Fastly, in which case everything loads quickly as I’d expect)

URL: GET hxxps://images.gog-statics.com/5ad0cce068c7a0d406a766e7c7d0c7ff95e712464de04902f1003bf328b17bcc_product_tile_80x114_2x.webp
Transferred 5.94kB
x-served-by: cache-fra-eddf8230081-FRA, cache-dfw-kdfw8210128-DFW
timings:
Blocked: 42 ms
DNS Resolution: 0 ms
Connecting: 0 ms
TLS Setup: 0 ms
Sending: 0 ms
Waiting: 452 ms
Receiving: 12.77s

URL GET hxxps://f.vimeocdn.com/cms/_next/static/chunks/pages/_app-23d50a50b5fd353e.js
Transferred: 652.79 kB
x-served-by: cache-iad-kcgs7200116-IAD, cache-dfw-kdfw8210124-DFW
timings:
Blocked: 199 ms
DNS Resolution: 0 ms
Connecting: 0 ms
TLS Setup: 0 ms
Sending: 0 ms
Waiting: 644 ms
Receiving: 33.71 s

I just collected those data points in the last hour or so; members of my household report anecdotally that it seems to have been happening over at least the past 3 days, usually a lot worse in the evening, and not as noticable in the mornings (Pacific timezone). Also, we tried several VPN endpoints, in the US and Europe, and none of them exhibited this slowness.

I had to obfuscate the https to hxxps to get past the “2 links per post” limit.

Let me know if there’s any other information I can provide to help debug this.

Corresponding network traces (replacing periods with underscores to try to bypass the “2 links per post” error):

mtr -c 20 -w -r shared.fastly.steamstatic_com
Start: 2025-01-20T20:56:35-0800
HOST: MacBookPro_lan Loss% Snt Last Avg Best Wrst StDev
1.|-- amplifi_lan 0.0% 20 8.8 4.5 1.9 33.5 7.0
2.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
3.|-- 216-165-242-37.championbroadband_com 0.0% 20 18.6 17.9 11.4 29.7 4.5
4.|-- 209.249.150.73.available.above_net 0.0% 20 24.0 20.5 10.8 48.8 9.6
5.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
6.|-- ae12.cs2.dfw2.us.zip.zayo_com 0.0% 20 42.9 52.8 42.3 72.0 7.8
7.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
8.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
9.|-- 151.101.3_52 15.0% 20 132.4 131.4 123.1 153.4 7.8
(ChampionBroadband is the old name of my ISP, GiggleFiber)

mtr -c 20 -w -r images.gog-statics_com
Start: 2025-01-20T21:01:49-0800
HOST: MacBookPro_lan Loss% Snt Last Avg Best Wrst StDev
1.|-- amplifi_lan 0.0% 20 2.5 2.7 1.9 5.0 0.8
2.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
3.|-- 216-165-242-37.championbroadband.com 0.0% 20 24.6 20.7 11.1 39.8 7.2
4.|-- 209.249.150.73.available.above_net 0.0% 20 15.2 22.2 12.5 54.3 10.1
5.|-- ae26.cs2.lax112.us.zip.zayo_com 95.0% 20 54.9 54.9 54.9 54.9 0.0
6.|-- ae12.cs2.dfw2.us.zip.zayo_com 95.0% 20 46.1 46.1 46.1 46.1 0.0
7.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
8.|-- 140.248.127_96 0.0% 20 60.3 52.9 46.6 68.4 5.5
9.|-- 151.101.193_55 5.0% 20 149.7 134.8 124.3 160.2 9.8

mtr -c 20 -w -r f.vimeocdn_com
Start: 2025-01-20T21:03:59-0800
HOST: MacBookPro_lan Loss% Snt Last Avg Best Wrst StDev
1.|-- amplifi_lan 0.0% 20 2.6 2.8 2.0 6.0 0.9
2.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
3.|-- 216-165-242-37.championbroadband_com 0.0% 20 16.1 21.7 12.3 38.8 7.3
4.|-- 209.249.150.73.available.above_net 0.0% 20 31.4 25.6 12.5 91.0 17.1
5.|-- ae25.cs1.lax112.us.zip.zayo_com 0.0% 20 45.2 54.7 45.2 114.2 14.6
6.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
7.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
8.|-- ??? 100.0 20 0.0 0.0 0.0 0.0 0.0
9.|-- 151.101.128_217 20.0% 20 126.2 131.4 124.3 141.5 5.5

Can you visit https://www.fastly-debug.com/ and take the generated text block to https://support.fastly.com and create a report in that portal?

Thanks! It’s happening again, so I just opened service case #877013, with the same title as this post.

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I might be hitting something similar. I noticed that repeated fetches (even with DNS round-robin hitting the same Fastly IP) are intermittently slow. So it’s not unique per IP.

I only see it from our colo in Austin, not from other sites (ISP is Cogent). Opened support ticket # 878003 but attaching the same repro screenshot here as that ticket.

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Fastly support suggested that it might be due to using Cloudflare’s DNS server, they thought that they weren’t able to geolocate me. So I turned off Firefox’s “DNS over HTTPS”, and made sure my DNS server was pointing at my wifi router, which in turn is pointing at my ISP’s DNS servers. Still taking 3 minutes to download a 1MB file, and 30 seconds to download a 10kb file via their DFW POP.

Fastly support said their network team made changes, and now even on Cloudflare DNS I’m not seeing the slowdown, and I’m getting connected to their LAX POP instead of DFW.