It depends what you need in your datacenters! If you just want servers, and don't care about doing something like anycast, you can find a bunch of local dedicated server providers in a bunch of cities and go to town. But you can't get them all from one provider, really, not with any kind of reasonable budget.
You _could_ buy colo from a place like Equinix in a bunch of cities, and then either use their transit or buy from other transit providers.
But also, unmetered bandwidth isn't a very sustainable service, so I'm curious what you're after? You're usually either going to have to pay for usage, or pay large monthly fixed prices to get reasonable transit connections in each datacenter.
In our case, we're constrained by Anycast. To expand past the 17 usual cities you end up needing to do your own network engineering which we'd rather not do yet.
It is anycast that I'm going after. Requirement for unmetered bandwidth (or cheaper than AWS et al) is because of the kind of workloads (TURN relays, proxy, tunnels etc) we'd deal with gets expensive, otherwise. For another related workload, per-request pricing gets expensive, again, due to the nature of the workload (to the tune 100k requests per user per month).
So far, for the former (TURN relays etc), I've found using AWS Global Accelerator and/or GCP's GLB to be the easiest way to do anycast but the bandwidth is slightly on the expensive side. Fly.io matches the pricing in terms of network bandwidth (as promised on the website), so that's a positive but GCP/AWS have a wider footprint. Cloudflare's Magic Transit is another potential solution, but requires an enterprise plan and one needs to bring-your-own-anycast-IP and origin-servers.
For the latter (latency-sensitive workload with ~100k+ reqs / month), Cloudflare Workers (200+ locations minus China) are a great fit though would get expensive once we hit a certain scale. Plus, they're limited to L7 HTTP reqs, only. Whilst, I believe, fly.io can do L4.
Does adding an extra 100ms to the response time cost you that much business wise?
As for colos, it depends on scale. If you have 30k servers world wide, it pays to have someone manage the contracts for you. If not it pays to go for the painful arseholes like vodaphone, or whoever bought Cable & wireless's stuff.
as for security, it gets very difficult. You need to make sure that each machine is actually running _what_ you told it, and know if someone has inserted a hypervisor shim between you and your bare metal.
none of that is off the shelf.
Which is why people pay the big boys, so that they can prove chain of custody and have very big locks on the cages.
K8s gives you scheduling and a datastore. For a large globally distributed system its going to scale like treacle.
I have come across fly.io, Vultr, Scaleway, Stackpath, Hetzner, and OVH but either they are expensive (in that they charge for bandwidth and uptime) or do not have a wide enough foot-print.
I guess colos are the way to go, but how does one work with colos, allocate servers, deploy to them, ensure security and uptime and so on from a single place, 'cause dealing with them individually might slow down the process? Is there a tooling that deals with multi-colos like the ones for multi-cloud like min.io, k8s, Triton etc;