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Durable Objects — now Generally Available


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Full Stack Week is all about how developers are embracing the power of Cloudflare’s network to build entire applications that are global by default. The promise of Workers isn’t just improved latency — it’s fundamentally different programming paradigms that make developer’s lives easier and applications more resilient.

Last year, we announced Durable Objects — Cloudflare’s approach to coordinating state across Workers running at Cloudflare’s edge. Durable Objects let developers implement previously complex applications, like collaborative whiteboarding, game servers, or global queues, in just a few lines of code.

Today, we’re announcing that Durable Objects are generally available and production-ready for you to use!

What makes Durable Objects so cool?

For many traditional applications, state coordination happens through a database. Applications built on Workers present some unique challenges for a database — namely needing to handle global scale out-of-the-box and heavy concurrency that could lead to frequent transaction rollbacks when coordinating on shared keys. Databases themselves are hard to configure and scale, especially at global scale, so developers would need to tweak their database specifically for Workers’ access patterns.

Durable Objects present a simpler paradigm: write a JavaScript class, and your application can create named instances of that class — which are guaranteed to be unique across Cloudflare’s entire network. That instance is a Durable Object — Workers (and other Durable Objects!) can send messages to it via its ID. The Durable Object processes messages in-order and on a single-thread, allowing for coordination across messages. We also provide a strongly consistent storage API, which can store key-value pairs the object needs to make durable.

Take, for example, an online document editor.  A typical architecture would save the state of the document in a database and have users persist changes there.  This makes collaboration difficult, though — how can multiple users ensure that they all see the latest copy of changes to the document?

With Durable Objects, this is a much simpler problem.  By writing a Document class, you store the state of each document in-memory in a Durable Object.  As users connect, they’ll see the latest copy of the document — and can make their changes in-sync with other users. When users leave the document, the Durable Object will leave memory and stop incurring charges, while its state is persisted durably.  There’s no networking to configure, database to manage, or autoscaling policy to implement — it all just works.

While individual objects are single-threaded, Durable Objects’ design means a collection of objects can scale effectively infinitely. An object’s lifecycle is managed for you, meaning there’s no clean-up tasks to run or systems to scale down — Durable Objects can instantly scale to hundreds of thousands of requests per second, then scale back down with no developer interaction.

What have we been building since announcing Early Access?

First, we’ve kept busy improving reliability and performance. Durable Objects are behind a number of new products being developed at Cloudflare, including powering R2 storage and Cloudflare Waiting Room.

Specifically, Waiting Room uses Durable Objects to provide a strongly consistent view of the current number of users attempting to access a given site globally.  Storing this frequently updated state in a traditional database would be difficult to scale and be significantly harder to run globally.

Our customers have also embraced Durable Objects. We’ve seen a major gaming company build their new backend architecture on Durable Objects — coordinating both individual game state and multiplayer game lobbies.  The ability to dynamically scale without managing servers or databases made Durable Objects an easy choice for them, letting them grow their game with a relatively small team.

Customers have built more applications — from status page monitors to collaborative whiteboard applications.  We’ve seen particular interest in using Durable Objects with WebSockets to create entirely responsive applications and have published a reference architecture to help customers build this out further.

We’ve also gotten better at operating the system, particularly in response to large volumes of requests. Durable Objects can now serve hundreds of thousands of requests per second across objects, and hundreds of requests on a single object, making them production-ready for even the most demanding customers.

We’ve shipped Jurisdictional Restrictions, which bring the simplicity of scaling Durable Objects to compliance by letting developers tag a Durable Object with a region, ensuring it processes and stores data in that region.

We added a cache in front of Durable Object storage requests, making read and write operations blazing fast while also making it easier to write correct concurrent code.

Beyond that, we’ve made a number of smaller improvements that included simplified uploads of new Durable Objects classes, a UI in the dashboard and support for wrangler dev and wrangler tail for live debugging.

What’s next for Durable Objects?

We’re continuing to work on making Durable Objects the easiest platform for building infinitely-scalable applications.

Today, Durable Objects scale well when objects can be partitioned, but individual objects are limited to a single execution thread. Many workloads could be scaled across multiple threads, providing read-only access to an object’s state and choosing to only synchronize when mutating state. We’re calling this replication for Durable Objects, and we’re working on it now.

We’re also working on adding an API for a guaranteed callback to a Durable Object, letting developers wake a Durable Object at a specified time in the future to run a function. This simplifies lifecycle management, making it easy to build primitives like reliable queues on top of Durable Objects.

We’re also looking into how to better geo-distribute objects, including the vision for automatic migration of objects we talked about in our initial announcement.

Have something you’d like to see us add? Shoot us an email or a tweet!

How do I use Durable Objects?

Head over to the Cloudflare Dashboard to enable Durable Objects and opt in to pricing, then check out our sample chat application and reference architecture here!

Happy building!

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Greg McKeon|@wegmckeon

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