Cloudflare takes in the Deno team behind celld, the open-source implementation of Workers and Durable Objects

Leaving a platform takes two things: a runtime that executes your code somewhere else, and replacements for the services the platform wired in. Workers has had the first for some time. Its runtime, workerd, is open source, and Cloudflare says it is the same code it runs in production ^[16]. "As a matter of fact, we have former customers that migrated away from us by using workerd," Cloudflare wrote in the joint post Kenton Varda co-authored with Deno ^[17][15].

Scaled Durable Objects were the missing piece. Cloudflare says it has wanted to fix workerd's single-instance limit since the original release, and the TODO comments in the code go back that far ^[8]. It names its production Durable Object routing as the obstacle ^[8]. The services around the runtime are thin as well. "Frankly, we haven't done a great job of building out the ecosystem of adjacent services and tooling to make it really work," the post says ^[9]. A few teams run workerd in production, "but so far, not that many," by Cloudflare's own account ^[18].

Deno released celld in August to close that gap ^[1][4]. At Cloudflare, the Deno team will combine that work with the Workers and Durable Objects teams ^[14]. It will also work toward integrating rusty_v8 into workerd ^[11]. "We want to make this programming model the default way to build servers, whether you run on Cloudflare's network or your own infrastructure," Deno wrote ^[10].

So the people who wrote the scaled exit now work for the platform it exits ^[2]. I think that matters less than it first appears, and Cloudflare's own post gives the reason. When Cloudflare pitched Workers for Platforms to customers including Shopify in 2022, those customers said they could not build on it unless the runtime was open source, so Cloudflare open-sourced it ^[19]. An exit that stays open because large buyers demand one lasts as long as they keep demanding it. I'd weight that requirement above the post's broader claim that Workers differs from other platforms because it is better ^[13].

Until now, celld's independent steward was Deno. Deno is ending separate work on its own runtime and hosting service ^[14]. Deploy shuts down six months before the runtime's support year runs out ^[21]. Paying Deploy customers get migration support to Cloudflare Workers, so anyone who picked Deploy as the non-Cloudflare option is being moved onto Cloudflare ^[7].

Deno's post does not say whether celld stays a separate project or folds into workerd, and it does not include a date for scaled Durable Objects outside Cloudflare. A Durable Objects app can only move if that code runs objects on more than one machine you control. The bindings Workers uses to reach external resources also have to point at services you can host ^[20]. Cloudflare's post says it released the runtime and hoped the community would adapt it to every environment, and that did not happen ^[12].