Gotcha, honestly that feels pretty niche to me, which might be a good place for a startup to start.
I can't think of many back-end applications between purely static content (just use a CDN) and needs a database connection. Probably video game servers, where you don't need the game state to be (immediately) stored/accessed globally.
We've been talking to a lot of startups doing communications tools, especially for remote work.
Lots of full stack apps benefit from app servers + redis cache in different regions. They need a database connection, but if they're already done the work to minimize DB round trips they might just work with no code changes.
There are also a bunch of folks doing really dynamic video and image delivery. Where an individual user gets an entirely unique blob of binary data.
I could see IoT device 'acceleration' to be a significant potential use-case. Something with a tiny bill of materials for the device itself, offloading any non-trivial processing to a virtual device on the closest 'real' infrastructure you can get. Especially for something human-interactive, you would want to be very aggressive about minimizing latency.
Also, depending on how tight the limits are for VM lifetime / bandwidth / outbound connections, I could see using these as a kind of virtual NIC / service mesh type thing for consumer-grade internet connections, to restore the inbound routing capabilities precluded by carrier-grade NAT and avoid their traffic discrimination, as well as potentially on-boarding to higher-quality transit as early as possible for use when accessing latency-sensitive services further 'interior' to the cloud.
These are great. IoT seems like a thing you could do but that's a really specific use case I hadn't even considered.
The second example would be interesting to try. There's no real limit on VM lifetime or outbound connections, bandwidth is more of a budget problem. VMs are ephemeral, so they _can_ go away but we're all happier if they just run forever.
I can't think of many back-end applications between purely static content (just use a CDN) and needs a database connection. Probably video game servers, where you don't need the game state to be (immediately) stored/accessed globally.