[SonuSitebot]

That’s a super exciting use case — running millions of test scripts across a multi-host, multi-region setup is no small feat. You're spot on about Testcontainers — it's elegant for one-off, isolated runs (like in CI), but when you're pushing at scale, the overhead of spinning up and tearing down containers for every single test can start to hurt. In high-throughput environments, most scalable setups I’ve seen shift towards a pre-warmed pool of sandbox containers — essentially keeping a fleet of "hot" containers alive and routing tasks into them via docker exec. You lose a bit of isolation granularity but gain massively in performance. You could even layer in a custom scheduler (Redis- or NATS-backed maybe?) that tracks container load and availability across hosts. Pair that with a smart TTL+health checker, and you can recycle containers efficiently without zombie buildup. Also — curious if you've explored running lighter-weight VMs (like Firecracker or Kata Containers) instead of full Docker containers? They can offer tighter isolation with decent spin-up times, and could be a better fit for multi-tenant test runs at this scale. Would love to nerd out more on this — are you planning to open source anything from your infra? Or even just blog about the journey? I feel like this would resonate with a lot of folks in the testing/devops space.