Same stateful trick, now with your own infrastructure
We've got good news for developers who are enamored with Cloudflare Workers and Durable Objects but don’t want to be tied into that company’s backend infrastructure. Last week, Node.js creator Ryan Dahl unveiled his latest project, celld, which he described on X as “a self-hosted, distributed Durable Objects and Workers implementation.”Dahl’s celld model is compatible with Cloudflare’s Workers and Durable Objects’ JavaScript APIs, but he claims that it is much less expensive to run.The project is no mere budget-minded open source rip. On celld’s web page, Dahl and his team characterize their replication of the Durable Objects architecture as a “love letter.”
Cloudflare’s Durable Objects is a single-threaded object with a unique global ID and its own storage, where user data is stored in its own copy of SQLite. It runs on the Cloudflare serverless Workers runtime, which runs apps embedded in isolates—a type of lightweight virtual machine supported by Google's V8 JavaScript engine.
First devised by Kenton Varda and Cloudflare, Durable Objects is “one of the best primitives distributed systems has been handed in years,” celld’s creators write. Unlike traditional serverless platforms like AWS Lambda, the Durable Objects model co-locates the data with compute, while using single-threaded execution to eliminate complex concurrency issues. “A primitive this good deserves to run anywhere,” the celld page states. Serverless but statefulSince its introduction in 2020, Durable Objects has been used to build low-latency, highly distributed Web applications. It is a stateful serverless execution environment, a data cache that can also do computation. Using the WebSocket API, the Durable Object can connect many simultaneous users at once in a live environment. WebSockets’ Hibernate mode can put the object to sleep, so cloud bills don’t accrue when no one uses the app. As a result, the stateful serverless model is best suited for real-time collaborative applications, such as multi-player games, team productivity apps and AI agents. Cloudflare uses Durable Objects for its serverless SQL service and AI Gateway.One YouTube tutorialist explained that using Durable Objects allowed him to eliminate an entire stack of tools (Amazon API Gateway, Apache Kafka, Redis, AWS Lambda and EventBridge, Apache Airflow and Spark all get name-dropped) because Durable Objects can handle all these functionalities “at a smaller scale.” Giving Durable Objects an open source home
