Skip to content
Cloudflare Docs

Pricing

Durable Objects can incur two types of billing: compute and storage.

On Workers Free plan:

  • If you exceed any one of the free tier limits, further operations of that type will fail with an error.
  • Daily free limits reset at 00:00 UTC.

Compute billing

Durable Objects are billed for duration while the Durable Object is active and running in memory. Requests to a Durable Object keep it active or creates the object if it was inactive, not in memory.

Free planPaid plan
Requests100,000 / day1 million, + $0.15/million
Includes HTTP requests, RPC sessions1, WebSocket messages2, and alarm invocations
Duration313,000 GB-s / day400,000 GB-s, + $12.50/million GB-s4,5

Footnotes

1 Each RPC session is billed as one request to your Durable Object. Every RPC method call on a Durable Objects stub is its own RPC session and therefore a single billed request.

RPC method calls can return objects (stubs) extending RpcTarget and invoke calls on those stubs. Subsequent calls on the returned stub are part of the same RPC session and are not billed as separate requests. For example:

let durableObjectStub = OBJECT_NAMESPACE.get(id); // retrieve Durable Object stub
using foo = await durableObjectStub.bar(); // billed as a request
await foo.baz(); // treated as part of the same RPC session created by calling bar(), not billed as a request
await durableObjectStub.cat(); // billed as a request

2 A request is needed to create a WebSocket connection. There is no charge for outgoing WebSocket messages, nor for incoming WebSocket protocol pings ↗. For compute requests billing-only, a 20:1 ratio is applied to incoming WebSocket messages to factor in smaller messages for real-time communication. For example, 100 WebSocket incoming messages would be charged as 5 requests for billing purposes. The 20:1 ratio does not affect Durable Object metrics and analytics, which reflect actual usage.

3 Application level auto-response messages handled by state.setWebSocketAutoResponse() will not incur additional wall-clock time, and so they will not be charged.

4 Duration is billed in wall-clock time as long as the Object is active, but is shared across all requests active on an Object at once. Calling accept() on a WebSocket in an Object will incur duration charges for the entire time the WebSocket is connected. It is recommended to use the WebSocket Hibernation API to avoid incurring duration charges once all event handlers finish running. Note that the Durable Object will remain active for 10 seconds after the last client disconnects. For a complete explanation, refer to When does a Durable Object incur duration charges?.

5 Duration billing charges for the 128 MB of memory your Durable Object is allocated, regardless of actual usage. If your account creates many instances of a single Durable Object class, Durable Objects may run in the same isolate on the same physical machine and share the 128 MB of memory. These Durable Objects are still billed as if they are allocated a full 128 MB of memory.

Storage billing

The Durable Objects Storage API is only accessible from within Durable Objects. Pricing depends on the storage backend of your Durable Objects.

  • SQLite-backed Durable Objects (recommended): SQLite storage backend is recommended for all new Durable Object classes. Workers Free plan can only create and access SQLite-backed Durable Objects.
  • Key-value backed Durable Objects: Key-value storage backend is only available on the Workers Paid plan.

SQLite storage backend

Workers Free planWorkers Paid plan
Rows reads 1,25 million / dayFirst 25 billion / month included + $0.001 / million rows
Rows written 1,2,3,4100,000 / dayFirst 50 million / month included + $1.00 / million rows
SQL Stored data 55 GB (total)5 GB-month, + $0.20/ GB-month

Footnotes

1 Rows read and rows written included limits and rates match D1 pricing, Cloudflare's serverless SQL database.

2 Key-value methods like get(), put(), delete(), or list() store and query data in a hidden SQLite table and are billed as rows read and rows written.

3 Each setAlarm() is billed as a single row written.

4 Deletes are counted as rows written.

5 Durable Objects will be billed for stored data until the data is removed. Once the data is removed, the object will be cleaned up automatically by the system.

Key-value storage backend

Workers Paid plan
Read request units1,21 million, + $0.20/million
Write request units31 million, + $1.00/million
Delete requests41 million, + $1.00/million
Stored data51 GB, + $0.20/ GB-month

Footnotes

1 A request unit is defined as 4 KB of data read or written. A request that writes or reads more than 4 KB will consume multiple units, for example, a 9 KB write will consume 3 write request units.

2 List operations are billed by read request units, based on the amount of data examined. For example, a list request that returns a combined 80 KB of keys and values will be billed 20 read request units. A list request that does not return anything is billed for 1 read request unit.

3 Each setAlarm is billed as a single write request unit.

4 Delete requests are unmetered. For example, deleting a 100 KB value will be charged one delete request.

5 Durable Objects will be billed for stored data until the data is removed. Once the data is removed, the object will be cleaned up automatically by the system.

Requests that hit the Durable Objects in-memory cache or that use the multi-key versions of get()/put()/delete() methods are billed the same as if they were a normal, individual request for each key.

Compute billing examples

These examples exclude the costs for the Workers calling the Durable Objects. When modelling the costs of a Durable Object, note that:

  • Inactive objects receiving no requests do not incur any duration charges.
  • The WebSocket Hibernation API can dramatically reduce duration-related charges for Durable Objects communicating with clients over the WebSocket protocol, especially if messages are only transmitted occasionally at sparse intervals.

Example 1

This example represents a simple Durable Object used as a co-ordination service invoked via HTTP.

  • A single Durable Object was called by a Worker 1.5 million times
  • It is active for 1,000,000 seconds in the month

In this scenario, the estimated monthly cost would be calculated as:

Requests:

  • (1.5 million requests - included 1 million requests) x $0.15 / 1,000,000 = $0.075

Compute Duration:

  • 1,000,000 seconds * 128 MB / 1 GB = 128,000 GB-s
  • (128,000 GB-s - included 400,000 GB-s) x $12.50 / 1,000,000 = $0.00

Estimated total: ~$0.075 (requests) + $0.00 (compute duration) + minimum $5/mo usage = $5.08 per month

Example 2

This example represents a moderately trafficked Durable Objects based application using WebSockets to broadcast game, chat or real-time user state across connected clients:

  • 100 Durable Objects have 50 WebSocket connections established to each of them.
  • Clients send approximately one message a minute for eight active hours a day, every day of the month.

In this scenario, the estimated monthly cost would be calculated as:

Requests:

  • 50 WebSocket connections * 100 Durable Objects to establish the WebSockets = 5,000 connections created each day * 30 days = 150,000 WebSocket connection requests.
  • 50 messages per minute * 100 Durable Objects * 60 minutes * 8 hours * 30 days = 72,000,000 WebSocket message requests.
  • 150,000 + (72 million requests / 20 for WebSocket message billing ratio) = 3.75 million billing request.
  • (3.75 million requests - included 1 million requests) x $0.15 / 1,000,000 = $0.41.

Compute Duration:

  • 100 Durable Objects * 60 seconds * 60 minutes * 8 hours * 30 days = 86,400,000 seconds.
  • 86,400,000 seconds * 128 MB / 1 GB = 11,059,200 GB-s.
  • (11,059,200 GB-s - included 400,000 GB-s) x $12.50 / 1,000,000 = $133.24.

Estimated total: $0.41 (requests) + $133.24 (compute duration) + minimum $5/mo usage = $138.65 per month.

Example 3

This example represents a horizontally scaled Durable Objects based application using WebSockets to communicate user-specific state to a single client connected to each Durable Object.

  • 100 Durable Objects each have a single WebSocket connection established to each of them.
  • Clients sent one message every second of the month so that the Durable Objects were active for the entire month.

In this scenario, the estimated monthly cost would be calculated as:

Requests:

  • 100 WebSocket connection requests.
  • 1 message per second * 100 connections * 60 seconds * 60 minutes * 24 hours * 30 days = 259,200,000 WebSocket message requests.
  • 100 + (259.2 million requests / 20 for WebSocket billing ratio) = 12,960,100 requests.
  • (12.9 million requests - included 1 million requests) x $0.15 / 1,000,000 = $1.79.

Compute Duration:

  • 100 Durable Objects * 60 seconds * 60 minutes * 24 hours * 30 days = 259,200,000 seconds
  • 259,200,000 seconds * 128 MB / 1 GB = 33,177,600 GB-s
  • (33,177,600 GB-s - included 400,000 GB-s) x $12.50 / 1,000,000 = $409.72

Estimated total: $1.79 (requests) + $409.72 (compute duration) + minimum $5/mo usage = $416.51 per month

Example 4

This example represents a moderately trafficked Durable Objects based application using WebSocket Hibernation to broadcast game, chat or real-time user state across connected clients:

  • 100 Durable Objects each have 100 Hibernatable WebSocket connections established to each of them.
  • Clients send one message per minute, and it takes 10ms to process a single message in the webSocketMessage() handler. Since each Durable Object handles 100 WebSockets, cumulatively each Durable Object will be actively executing JS for 1 second each minute (100 WebSockets * 10ms).

In this scenario, the estimated monthly cost would be calculated as:

Requests:

  • 100 WebSocket connections * 100 Durable Objects to establish the WebSockets = 10,000 initial WebSocket connection requests.
  • 100 messages per minute1 * 100 Durable Objects * 60 minutes * 24 hours * 30 days = 432,000,000 requests.
  • 10,000 + (432 million requests / 20 for WebSocket billing ratio) = 21,610,000 million requests.
  • (21.6 million requests - included 1 million requests) x $0.15 / 1,000,000 = $3.09.

Compute Duration:

  • 100 Durable Objects * 1 second2 * 60 minutes * 24 hours * 30 days = 4,320,000 seconds
  • 4,320,000 seconds * 128 MB / 1 GB = 552,960 GB-s
  • (552,960 GB-s - included 400,000 GB-s) x $12.50 / 1,000,000 = $1.91

Estimated total: $3.09 (requests) + $1.91 (compute duration) + minimum $5/mo usage = $10.00 per month

1 100 messages per minute comes from the fact that 100 clients connect to each DO, and each sends 1 message per minute.

2 The example uses 1 second because each Durable Object is active for 1 second per minute. This can also be thought of as 432 million requests that each take 10 ms to execute (4,320,000 seconds).

Frequently Asked Questions

Does an empty table / SQLite database contribute to my storage?

Yes, although minimal. Empty tables can consume at least a few kilobytes, based on the number of columns (table width) in the table. An empty SQLite database consumes approximately 12 KB of storage.

Does metadata stored in Durable Objects count towards my storage?

All writes to a SQLite-backed Durable Object stores nominal amounts of metadata in internal tables in the Durable Object, which counts towards your billable storage.

The metadata remains in the Durable Object until you call deleteAll().

When does a Durable Object incur duration charges?

A Durable Object incurs duration charges as long as the JavaScript object is held in memory. Once an object has been evicted from memory, the next time it is needed, it will be recreated (calling the constructor again). There are two factors which decide when an object may be evicted from memory: hibernatability and existence of clients.

A Durable Object is considered hibernatable any time that it is not waiting for any I/O or callbacks that depend on the in-memory state.

  • For example, if an object calls fetch() and awaits the response, it is considered to be waiting for I/O, and so cannot hibernate.

  • Less obvious to a user, if an object calls setTimeout() to schedule a callback in the future - no matter how far in the future - then it is considered non-hibernatable, since there would be no way to recreate the callback after hibernating.

  • Additionally, if the Durable Object has received an incoming request and has not fully responded yet, then it cannot be hibernated, because hibernating would mean losing track of the async function which is eventually supposed to return a response to that request.

  • As an exception, a WebSocket request which has explicitly been accepted using the [WebSocket hibernation API](/durable-objects/best-practices/websockets/#websocket-hibernation-api allows a Durable Object to hibernate even while the WebSocket is still connected.

Once a Durable Object has been in a hibernatable state for 10 consecutive seconds, it hibernates, and duration billing stops.

Even if a Durable Object never becomes hibernatable, it will still be evicted once all clients have gone away. A Durable Object is considered to have clients if any other Worker currently holds a stub pointing to the Durable Object, or is waiting for a response from the Durable Object. An incoming WebSocket connection counts as a client. If the object is currently responding to an alarm event, this also counts as having a client. When not hibernatable, a Durable Object will be evicted from memory after it has had no client for 70-140 seconds (the exact interval varies). But again, if the object is hibernatable, then the 10-second hibernation timeout takes precedence and the 70-140 second no-client timeout is moot.