Ryan Dahl Releases Celld, a Self-Hosted Open-Source Alternative to Cloudflare's Durable Objects
Node.js and Deno creator Ryan Dahl has open-sourced celld, letting developers run Cloudflare's Durable Objects and Workers APIs on their own S3-backed infrastructure.
Overview
Ryan Dahl, the creator of Node.js and Deno, has released celld, an open-source daemon that lets developers run Cloudflare’s Workers and Durable Objects JavaScript APIs on their own infrastructure instead of Cloudflare’s, according to The Register. Dahl’s project is compatible with Cloudflare’s Workers and Durable Objects APIs but claims it costs significantly less to operate, as The Register reported.
What We Know
According to celld’s own GitHub repository, the project “is an open-source daemon that runs Cloudflare Workers and Durable Objects on your own machines.” Each object is its own SQLite database, addressed by name and replicated to a storage bucket that the operator owns; the bucket can be S3-compatible or Google Cloud Storage, and “the nodes coordinate through that bucket alone, with no control plane and no consensus,” the repository states. Because every object is its own small database, the project’s documentation says “applications shard by construction — the contention and blast-radius failures of one shared database are designed out, not managed,” and “a cell that no node holds is inactive, and an inactive cell costs nearly nothing.”
The GitHub README explains that every celld node embeds the V8 JavaScript engine and executes Wrangler bundles, with the fleet sharing a single bucket that holds deployments, cell state, and ownership records. Object-storage compare-and-swap operations ensure that exactly one node owns a cell at a time, “without a membership protocol, failure detector, or consensus service.” celld continuously replicates each cell’s SQLite database to the bucket, and when a cell moves or an inactive cell activates, its new owner restores that database and resumes execution, making the bucket “the durable source of truth” while nodes remain replaceable.
Cloudflare’s own Durable Objects technology, which celld is modeled on, functions as a single-threaded object with a unique global ID and dedicated SQLite-backed storage, running on Cloudflare’s serverless Workers runtime inside V8 isolates, according to The Register. The technology was devised by Kenton Varda and Cloudflare, and celld’s creators describe it as “one of the best primitives distributed systems has been handed in years,” per the outlet. Unlike traditional serverless platforms such as AWS Lambda, the Durable Objects model co-locates data with compute while using single-threaded execution to avoid complex concurrency problems, The Register reported. Since 2020, Durable Objects has powered low-latency, distributed web applications, providing a stateful serverless environment that functions as a data cache capable of computation; its WebSocket API can connect many simultaneous users, and a Hibernate mode can suspend an object to prevent billing from accumulating while an app sits idle. Cloudflare uses Durable Objects internally for its serverless SQL service and its AI Gateway, The Register noted.
Dahl “promises this open source backend will be ‘orders of magnitude cheaper at scale’ than Durable Objects,” according to The Register. He estimated that 100 resident Durable Object cells cost $415 a month on Cloudflare, while the same workload on celld would run approximately $49 a month, built on a DigitalOcean S3-compatible bucket running on an 8 GB droplet, with savings expected to grow as workloads scale, the outlet reported. Cloudflare disputed those figures, telling The Register that the $415 monthly estimate would apply only if all the objects remained continuously active; if allowed to hibernate, the same 100 Durable Objects would cost just $20.65 a month on Cloudflare, according to a company spokesperson cited by the outlet.
celld replaces the Cloudflare backend with Amazon S3 or an equivalent object-storage service and runs on the Tokio Rust asynchronous runtime, giving each object its own SQLite copy just as Durable Objects does, The Register reported. The project is written in Rust and JavaScript and distributed under an Apache 2 license, according to both The Register and the project’s GitHub page, which lists the license as Apache-2.0. It runs JavaScript and TypeScript code directly, and The Register reported that, in theory, Rust, C/C++, Go, or Zig code could also execute through WebAssembly, which V8 supports with slight modifications. The GitHub repository offers a shell-script installer and container images published for Linux x86-64 and ARM64 architectures.
The GitHub repository states that pull requests are disabled: “Coding agents make it too easy to send a large, low-context change that costs maintainers more time than it saves.” It adds: “Thoughtful contributions are welcome; please understand the code, keep the patch focused, and respect the review time you are asking for,” directing contributors to send a patch by email rather than opening a pull request.
The release has already drawn attention beyond Dahl’s own following. One Hacker News reader wrote, “So happy to see support for running durable objects outside of one provider. Upvoted,” calling the durable-object concept a valuable abstraction, according to The Register. The outlet also noted that celld is not the only effort to move data closer to compute: Postgres provider Neon recently introduced Neon Functions, which similarly co-locates data and compute for long-running workloads.
Who Is Behind It
Dahl created Node.js, the JavaScript runtime that The Register described as powering “the world’s fastest web applications,” and is credited by the outlet as a world-leading expert in JavaScript I/O — a role in which he inadvertently popularized “callback hell,” the pattern where nested asynchronous callbacks make code difficult to follow. He later addressed those design issues with a second-generation runtime, Deno, The Register reported. celld is published under the same denoland organization on GitHub that hosts the Deno runtime, which previously reported work by Dahl’s team has continued to mature with releases like Deno 2.7.
What We Don’t Know
Dahl’s cost comparison and Cloudflare’s rebuttal rest on different assumptions about how continuously the underlying objects run, and neither figure has been independently benchmarked in a real-world, apples-to-apples deployment. It also remains to be seen how celld performs at the multi-region, high-availability scale that Cloudflare’s global network provides by default, since celld’s bucket-only coordination model has not yet been tested publicly at that scale.