Managing concurrency

Limit the number of concurrently running steps for your function with the concurrency configuration options. Setting an optional key parameter limits the concurrency for each unique value of the expression.

Read our concurrency guide for more information on concurrency, including how it works and any limits.

export default inngest.createFunction(
  {
    id: "sync-contacts",
    concurrency: {
      limit: 10,
    },
  }
  // ...
);

Setting concurrency limits are very useful for:

Handling API rate limits - Limit concurrency to stay within the rate limit quotas that are allowed by a given third party API.
Limiting database operations or connections
Preventing one of your user's accounts from consuming too many resources (see key)

Alternatively, if you want to limit the number of times that your function runs in a given period, the rateLimit option may be better for your use case.

Configuration

Name
concurrency
Type
number | object | [object, object]
Required
optional
Description
Options to configure concurrency. Specifying a number is a shorthand to set the limit property.
Properties
- Name
  limit
  Type
  number
  Required
  required
  Description
  The maximum number of concurrently running steps. A value of 0 or undefined is the equivalent of not setting a limit. The maximum value is dictated by your account's plan.
- Name
  scope
  Type
  'account' | 'env' | 'fn'
  Required
  optional
  Description
  The scope for the concurrency limit, which impacts whether concurrency is managed on an individual function, across an environment, or across your entire account.
  
  fn (default): only the runs of this function affects the concurrency limit
  
  env: all runs within the same environment that share the same evaluated key value will affect the concurrency limit. This requires setting a key which evaluates to a virtual queue name.
  
  account: every run that shares the same evaluated key value will affect the concurrency limit, across every environment. This requires setting a key which evaluates to a virtual queue name.
- Name
  key
  Type
  string
  Required
  optional
  Description
  An expression which evaluates to a string given the triggering event. The string returned from the expression is used as the concurrency queue name. A key is required when setting an env or account level scope.
  Expressions are defined using the Common Expression Language (CEL) with the original event accessible using dot-notation. Read our guide to writing expressions for more info. Examples:
  
  Limit concurrency to n (via limit) per customer id: 'event.data.customer_id'
  
  Limit concurrency to n per user, per import id: 'event.data.user_id + "-" + event.data.import_id'
  
  Limit globally using a specific string: '"global-quoted-key"' (wrapped in quotes, as the expression is evaluated as a language)

The current concurrency option controls the number of concurrent steps that can be running at any one time.

Because a single function run can contain multiple steps, it's possible that more functions than the concurrency limit are triggered, but only the set number of steps will ever be running.