Also, MicroVMs can't be exposed directly to the web. Your code running in them can only be executed via API calls with attached auth tokens - so if you wanted to host a public facing API or website with them you'd need to implement your own additional layer in front.

Something I appreciate about Fly (disclaimer: they support my work) is that the pricing is fixed - you pay $1.94/month (less if you suspend your machine) for the smallest instance, up to $976.25/month for the largest (16 CPUs, 128GB) plus predictable costs for volume storage.

The only variable outside your control is bandwidth, and that's unlikely to cause a nasty shock.

Contrast with any of the more "elastic" hosting providers - Vercel, Cloud Run - and you're much less likely to get a horrifying bill if something gets overly-crawled or goes viral.