Hi!

I'm using Astro 7 Route Cache with the Vercel adapter and have been testing it in production for several days.

I understand the purpose of maxAge, swr, and tags, and I've confirmed that tag invalidation works correctly.

For example, after calling invalidate(), I can observe:

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HIT → STALE → HIT

which matches the expected behavior.

However, I have a question about physical cache retention.

For example:

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Astro.cache.set({
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  maxAge: 60 * 60 * 24 * 365,
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});

Even with a very long maxAge, I often observe that pages become MISS after several hours (or after a period without traffic), resulting in a MISS response instead of HIT.

I'm trying to understand how Route Cache retention works on Vercel.

Specifically:

1. Is cache eviction based on access frequency?
2. Are maxAge and physical cache retention completely independent?
3. Does enabling swr affect cache retention, or does it only control stale-while-revalidate behavior?
4. Is the eviction policy documented anywhere?

I couldn't find any documentation describing how Route Cache entries are physically retained or evicted on Vercel, so I'd appreciate any clarification.

In practice, I found that Astro's prefetch often has a bigger impact on perceived performance than Route Cache, so I'm trying to better understand how Route Cache is intended to be used in production.

I'm not reporting a bug—I'm just trying to better understand how Route Cache behaves in production so I can choose appropriate maxAge and swr values.

Thanks!