How to Trigger AWS Lambda on a Schedule Using EventBridge

You can trigger a AWS Lambda function on a schedule by creating an EventBridge rule with a cron or rate expression and setting the Lambda function as the target. This lets your Lambda run automatically at fixed times or intervals without manual intervention.

Syntax

To trigger a Lambda on schedule, you create an EventBridge rule with a schedule expression and add your Lambda function as the target. The key parts are:

• ScheduleExpression: Defines when the Lambda runs, using rate() or cron() syntax.
• Targets: The Lambda function ARN that will be invoked.
• State: Enables or disables the rule.

bash

aws events put-rule --name MyScheduledRule --schedule-expression "rate(5 minutes)" --state ENABLED

aws events put-targets --rule MyScheduledRule --targets Id=1,Arn=arn:aws:lambda:region:account-id:function:MyFunction

Example

This example creates an EventBridge rule that triggers a Lambda function every day at 6:00 AM UTC using a cron expression.

bash

aws events put-rule --name DailyMorningTrigger --schedule-expression "cron(0 6 * * ? *)" --state ENABLED

aws events put-targets --rule DailyMorningTrigger --targets Id=1,Arn=arn:aws:lambda:us-east-1:123456789012:function:MyDailyFunction

aws lambda add-permission --function-name MyDailyFunction --statement-id DailyTriggerPermission --action 'lambda:InvokeFunction' --principal events.amazonaws.com --source-arn arn:aws:events:us-east-1:123456789012:rule/DailyMorningTrigger

Output

Rule created: DailyMorningTrigger
Targets added to rule: DailyMorningTrigger
Permission added to Lambda function: MyDailyFunction

Common Pitfalls

• Missing Lambda permission: You must add permission for EventBridge to invoke your Lambda, or the trigger will fail.
• Incorrect schedule expression: Using wrong cron syntax or rate format causes errors or unexpected schedules.
• Wrong region or ARN: The Lambda ARN and EventBridge rule must be in the same AWS region.
• Disabled rule: If the rule state is not ENABLED, the Lambda won't trigger.

bash

Wrong (missing permission):
aws events put-rule --name TestRule --schedule-expression "rate(1 hour)" --state ENABLED
aws events put-targets --rule TestRule --targets Id=1,Arn=arn:aws:lambda:us-east-1:123456789012:function:MyFunction

Right (add permission):
aws lambda add-permission --function-name MyFunction --statement-id TestRulePermission --action 'lambda:InvokeFunction' --principal events.amazonaws.com --source-arn arn:aws:events:us-east-1:123456789012:rule/TestRule

Quick Reference

Use these tips to set up scheduled Lambda triggers smoothly:

• Use rate(value unit) for simple intervals (e.g., every 5 minutes).
• Use cron(fields) for complex schedules (e.g., specific time of day).
• Always add Lambda permission for EventBridge to invoke your function.
• Keep Lambda and EventBridge rule in the same AWS region.
• Enable the rule to activate the schedule.

Key Takeaways

Create an EventBridge rule with a schedule expression to trigger Lambda on a schedule.

Add your Lambda function as a target to the EventBridge rule.

Grant EventBridge permission to invoke your Lambda function.

Use correct cron or rate syntax for the schedule expression.

Ensure the rule is enabled and in the same region as your Lambda.