I have a 1M page site with export const revalidate = 2592000. Every deployment completely invalidates my ISR cache, causing massive ISR writes + costs.
Evidence:
-
Dec 31 had 4 deploys → 2M (!!!) ISR writes (~$8) with only 20 actual site visits on the day. Jan 1 already has 500K writes in 1 hour. I dont even have 2M pages!
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I tested a specific URL before/after deploy - etag changed from “dyw7c1hf012e6g” to “3ivi8uvt5k2e64” and went from HIT to MISS. The trigger is changing translation files in
public/locales/*.json. -
Vercel analytics show 98% cache miss rate (257K misses / 272K requests).
My config: export const revalidate = 2592000, data wrapped in unstable_cache with 30-day revalidate, firewall rules active for bots. The docs say ISR cache persists across deployments, but mine clears completely every time. Is this expected? How do I prevent unnecessary ISR writes? What am I missing? My build logs show 30d revalidation but my cache still clears every time. I dont have any cache clearing configs in my vercel project settings.
Im on the pro plan. I’ve been trying to get support on this since Dec 12. I know its a busy month but I urgently need some help around this because of the extremely large number of ISR writes happening daily ballooning up my on demand costs.
Team URL: https://vercel.com/irfanahmds-projects
BUILD LOG SHOWS 30 DAY REVALIDATE
LAST 24 HRS FROM OBSERVABILITY
CURL BEFORE DEPLOYMENT (CACHE HIT - 01 Jan 2026 03:22:36 GMT)
┌[irfan@MacBookPro] [/dev/ttys000] [main 
]
└[~/Development/Projects/brainrot-3e9ea85fc277211a5cbf721ab5c51215db5a372b]> curl -I Community Manager (Affiliate Marketing) कवर लेटर प्रारूप - LockedIn
HTTP/2 200
age: 2
cache-control: public, max-age=3600
content-security-policy: frame-ancestors ‘self’ https://www.browserbase.com
content-type: text/html; charset=utf-8
date: Thu, 01 Jan 2026 03:22:36 GMT
etag: “dyw7c1hf012e6g”
referrer-policy: no-referrer
server: Vercel
strict-transport-security: max-age=63072000
vary: rsc, next-router-state-tree, next-router-prefetch, next-router-segment-prefetch
x-content-type-options: nosniff
x-frame-options: ALLOW-FROM https://www.browserbase.com
x-matched-path: /[locale]/[…slug]
x-nextjs-prerender: 1
x-nextjs-stale-time: 4294967294
x-powered-by: Next.js
x-vercel-cache: HIT
x-vercel-id: yul1::iad1::jf9w9-1767237759386-435481a3e529
content-length: 152754
CURL AFTER DEPLOYMENT (CACHE MISS - 01 Jan 2026 04:40:23 GMT)
┌[irfan@MacBookPro] [/dev/ttys000] [main]
└[~/Development/Projects/brainrot-3e9ea85fc277211a5cbf721ab5c51215db5a372b]> curl -I Community Manager (Affiliate Marketing) कवर लेटर प्रारूप - LockedIn
HTTP/2 200
age: 0
cache-control: public, max-age=3600
content-security-policy: frame-ancestors ‘self’ https://www.browserbase.com
content-type: text/html; charset=utf-8
date: Thu, 01 Jan 2026 04:40:23 GMT
etag: “3ivi8uvt5k2e64”
referrer-policy: no-referrer
server: Vercel
strict-transport-security: max-age=63072000
vary: rsc, next-router-state-tree, next-router-prefetch, next-router-segment-prefetch
x-content-type-options: nosniff
x-frame-options: ALLOW-FROM https://www.browserbase.com
x-matched-path: /[locale]/[…slug]
x-nextjs-prerender: 1
x-nextjs-stale-time: 4294967294
x-powered-by: Next.js
x-vercel-cache: MISS
x-vercel-id: yul1::iad1::48t2f-1767242423732-fd737724899d
content-length: 152716