# API rate limits

To ensure the stability of the Checkout.com platform for all users, we may apply rate limits to calls to our API.

Checkout.com uses adaptive rate limiting to avoid rate-limiting reasonable quantities of legitimate requests. This means you generally only experience rate limiting if our system is under exceptional load.

> **Information**
>
> Usage limits apply globally across your entire account. They are not applied individually to each authentication credential or sub-entity making the call.

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## Concurrent rate limits

Our concurrency rate limits specify the maximum number of simultaneous requests-per-second (RPS) you can make to our APIs:

- Read operations – 100 RPS
- Write operations – 100 RPS

These limits are calculated across all APIs.

Your rate limits may differ from the default values if:

- You've configured different limits with your account manager.
- We detect system abuse.

> **Information**
>
> We apply lower rate limits to our sandbox environment.

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## Handle rate limits

If you receive a `429` HTTP response, you may be experiencing rate limiting.

To minimize the impact to your integration, we recommend that you implement an automated retry mechanism for `429` responses. For example, you can schedule retries using an exponential backoff with jitter to periodically retry requests at increasing intervals.

We also recommend that you implement additional rate and traffic management logic on the client-side. For example, using a token bucket algorithm to determine how many requests to send to the API.

> **Information**
>
> If you experience frequent `429` responses, contact your account manager to discuss your integration requirements.

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## Load testing

If you perform load testing on your systems to cover increased throughput scenarios, you will likely experience rate-limiting.

If you have a complex integration with additional requirements, contact your account manager or [request support](https://dashboard.checkout.com/support/new?topic=case_integration&issue=case_integration_issue_other) and provide details. We may be able to:

- Accommodate temporary changes to your rate limit.
- Arrange for specific load-testing windows.
- Set up dedicated sandbox environments.

> **Information**
>
> We do not recommend load testing in our sandbox environment due to the reduced rate limit.