This is barely a cloud, since it only serves one particular purpose and everything runs in V8 isolates. Although they would need to ensure they're appropriately capping each tenant's compute and bandwidth; the article mostly doesn't get into that.

Fully AOT compilers for JavaScript are basically research projects rather than production-ready platforms, because the extensive dynamicity of JavaScript's semantics makes this a hard problem. (The most mature one I'm aware of is https://porffor.dev.) But even if that weren't the case, the thing Telegram is doing requires V8's low-overhead tenant isolation, so they're bound to V8's architectural choices. V8 does have APIs for code caching and startup snapshots; Telegram could be generating those at deploy time.