Hey HN, this is Nathan and Nicholas from Rivet (https://rivet.dev) – a fast, high-density, and scalable orchestrator for agentic workloads using the actor model. Rather than running a heavyweight sandbox per agent, each agent gets a lightweight actor backed by S3.

Actors provide a long-lived process for long agent turns, in-memory state for context, a WebSocket server for multiplayer, durable SQLite storage backed by S3, and hibernation when idle.

It's a similar model to Cloudflare Durable Objects, but it’s open source and self-hostable.

Here’s a video walkthrough: https://www.youtube.com/watch?v=3Ev6I7DOV9c

When we went through YC in 2023, we were building infrastructure for multiplayer games like Diep and Krunker. This involved heavily optimizing high-throughput matchmaking, real-time player messages, and blitz scaling. Through that process, we spent a lot of time on workloads where Postgres couldn't keep up with our throughput. We started out by hacking together Lua scripts on top of Redis, but this became too cumbersome to maintain and upgrade. This led us to extend our game server orchestrator to support what we call Rivet Actors today: many lightweight workers with in-memory state and durable storage. By using actors, we were able to serve tens of millions of monthly active users.