🎭Rivet Open-Sources Actor Orchestrator With 4.99 ms Cold Starts Under Apache 2.0

Your agent sandboxes just got 340x cheaper to run

Sandboxes are the expensive default for agent workloads, and Rivet is betting you don't need one per agent. It's an open-source orchestrator built on the actor model, and its p99 cold start is 4.99 ms. Sandboxes sit at 1.70 s. If you're running agents that each boot a container or VM, this is the part to pay attention to. Rivet Actors share a single node process, so one server can hold hundreds of thousands of them. Each actor keeps in-memory state, a SQLite database, WebSockets, and scheduling, addressed by key. They hibernate when idle without losing data, so you're not paying for quiet agents. The numbers: 72.4 KB per instance versus 512 MiB for a sandbox. Storage is 10.4x cheaper than replicated SSD. The control plane runs anywhere a container runs, and instances find each other through an object storage bucket, which is the only dependency. That bucket can be S3, GCS, Azure Blob, or any S3-compatible store. The catch? Rivet's pitch is partly a direct swipe at Cloudflare Durable Objects, and it's still early. Check whether your workload actually fits the actor model before you rewrite anything.