This limit is tied to the Org ID, and not to individual OAuth clients, users, or access tokens.

How the concurrency limit applies

1. Organization-wide limit
   The concurrency cap depends on the Zoho Desk edition being used. All OAuth-authenticated API requests from any client or integration count toward this limit.
   
   
2. Not applied per OAuth client or per access token
   If you use multiple OAuth clients or generate multiple tokens, they all draw from the same concurrency pool.
   
   
3. Applies to all API calls authenticated via OAuth
   Whether you call APIs using SDKs, custom apps, extensions, backend servers, or third-party integrations, every OAuth-authenticated request contributes to the limit.
   
   
4. Not applicable to the Zoho Desk UI
   Actions performed by agents or customers directly in the Desk web interface do not count toward concurrency usage. Even in large setups with hundreds of agents, UI activity will not affect your integration’s concurrency capacity.
   
   
5. Not API-specific
   The limit applies collectively across all Desk APIs. For example, simultaneous calls across Tickets, Contacts, Search, or any other module count together.

What happens if you exceed the limit

1. Incoming requests will be throttled (rejected), depending on system load.
2. API responses may indicate concurrency limit violations.
3. Normal behavior resumes automatically once ongoing requests decrease.

Zoho Desk does not enforce any request rate limits per access token. Access tokens are valid for 1 hour, after which they must be refreshed.

When can you purchase add-on credits 

You can purchase additional API credits in either of the following ways from the Zoho Store:

1. While buying or upgrading your plan

    When you purchase a new paid plan or upgrade your existing plan to a paid one, you can add API credits during the checkout process.

When purchasing credits, you can select between 1,000 and 5,000,000 credits per transaction.