isr

2 posts

Aug 19, 2026

The CDN cache fighting the ISR — and holding the TTFB at 3.6s

A wrong Cache-Control header in vercel.json was overriding the revalidate=1800 ISR setting and turning every cache expiry into two synchronous GitHub calls inside the TTFB. The story of how cold cache became warm: 3.6s down to 140ms.

portfolio nextjs isr

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Portfólio

Aug 19, 2026

O cache do CDN que brigava com o ISR — e segurava o TTFB em 3.6s

Um header Cache-Control errado no vercel.json sobrescrevia o revalidate=1800 do ISR e transformava a expiração do cache em duas chamadas síncronas ao GitHub dentro do TTFB. A história de como o cache frio virou quente: 3.6s pra 140ms.

portfolio nextjs isr

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The CDN cache fighting the ISR — and holding the TTFB at 3.6s

O cache do CDN que brigava com o ISR — e segurava o TTFB em 3.6s