What is the difference between AWS cron and standard cron?

AWS cron uses 6 fields (includes year) and requires `?` for either day-of-month or day-of-week. Standard cron uses 5 fields and allows `*` in both day fields.

Can I use rate expressions instead of cron?

Yes. For simple intervals, use `rate(5 minutes)` or `rate(1 hour)` instead of cron expressions. Rate expressions are simpler but less flexible.

What timezone does AWS cron use?

UTC only. EventBridge cron expressions always use UTC. Convert your desired local time accordingly.

How much does a scheduled Lambda cost?

EventBridge rules are free. Lambda pricing is based on invocations and duration. A function running every 5 minutes with 128MB and 1-second duration costs roughly $0.10/month.

Why is my Lambda not being triggered?

Check that the EventBridge rule is enabled, the Lambda permission is set correctly (events.amazonaws.com needs invoke permission), and the cron expression is valid. Use CloudWatch Logs to verify invocations.

intermediate 14 min read

How to Set Up Cron Jobs with AWS Lambda & EventBridge

Learn how to schedule AWS Lambda functions using EventBridge (CloudWatch Events) cron expressions. Covers console, CLI, CDK, SAM, and monitoring.

Prerequisites

AWS account
AWS CLI configured
Basic Lambda knowledge

How AWS Cron Scheduling Works

AWS uses Amazon EventBridge (formerly CloudWatch Events) to trigger Lambda functions on a schedule. You create a rule with a cron expression, and EventBridge invokes your Lambda function at the specified times.

AWS cron expressions use a 6-field format that includes a year field and requires the ? character for either day-of-month or day-of-week.

Quick Start: AWS Console

Step 1: Create a Lambda function in the AWS Console

Step 2: Add an EventBridge trigger:

Go to your Lambda function → Add trigger → EventBridge
Select "Create a new rule"
Rule type: Schedule expression
Expression: cron(0 9 ? * MON-FRI *) (weekdays at 9 AM UTC)

Step 3: Save and test

You can also test immediately using the "Test" button in the Lambda console.

AWS CLI Setup

bash

# Create the Lambda function
aws lambda create-function \
  --function-name my-scheduled-task \
  --runtime nodejs20.x \
  --handler index.handler \
  --zip-file fileb://function.zip \
  --role arn:aws:iam::123456789:role/lambda-role

# Create the EventBridge rule
aws events put-rule \
  --name my-schedule \
  --schedule-expression "cron(0 9 ? * MON-FRI *)"

# Add Lambda as the target
aws events put-targets \
  --rule my-schedule \
  --targets "Id"="1","Arn"="arn:aws:lambda:us-east-1:123456789:function:my-scheduled-task"

# Grant EventBridge permission to invoke Lambda
aws lambda add-permission \
  --function-name my-scheduled-task \
  --statement-id my-schedule-permission \
  --action lambda:InvokeFunction \
  --principal events.amazonaws.com \
  --source-arn arn:aws:events:us-east-1:123456789:rule/my-schedule

AWS CDK Setup

typescript

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as events from 'aws-cdk-lib/aws-events';
import * as targets from 'aws-cdk-lib/aws-events-targets';

const fn = new lambda.Function(this, 'ScheduledFunction', {
  runtime: lambda.Runtime.NODEJS_20_X,
  handler: 'index.handler',
  code: lambda.Code.fromAsset('lambda'),
  timeout: cdk.Duration.minutes(5),
});

new events.Rule(this, 'ScheduleRule', {
  schedule: events.Schedule.cron({
    minute: '0',
    hour: '9',
    weekDay: 'MON-FRI',
  }),
  targets: [new targets.LambdaFunction(fn)],
});

AWS Cron Expression Syntax

AWS uses a 6-field cron format:

cron(minute hour day-of-month month day-of-week year)

Key differences from standard cron:

6 fields (includes year)
? (question mark) is required for either day-of-month or day-of-week (you can't specify both)
L — last day (e.g., L in day-of-month = last day of month)
W — nearest weekday (e.g., 15W = nearest weekday to the 15th)
# — nth day (e.g., FRI#2 = second Friday)

Examples:

cron(0 9 ? * MON-FRI *) — Weekdays at 9 AM UTC
cron(*/5 * ? * * *) — Every 5 minutes
cron(0 0 1 * ? *) — First day of every month
cron(0 12 ? * 2#1 *) — First Monday at noon

Common AWS Cron Expressions

cron(*/5 * ? * * *) — Every 5 minutes
cron(0 * ? * * *) — Every hour
cron(0 0 ? * * *) — Daily at midnight UTC
cron(0 9 ? * MON-FRI *) — Weekdays at 9 AM UTC
cron(0 0 1 * ? *) — First day of every month
cron(0 0 ? * SUN *) — Every Sunday at midnight
cron(0 0 L * ? *) — Last day of every month

You can also use rate expressions for simple intervals:

rate(5 minutes)
rate(1 hour)
rate(1 day)

Try it Open in full editor

Every weekday at 9:00 AM

Next runs (UTC):

Mon, May 18, 2026 09:00

Tue, May 19, 2026 09:00

Wed, May 20, 2026 09:00

Monitoring with CloudWatch

Lambda metrics to watch:

Invocations — confirms your schedule is triggering
Errors — failed invocations
Duration — execution time (watch for approaching timeout)
Throttles — concurrency limit hit

Set up an alarm:

bash

aws cloudwatch put-metric-alarm \
  --alarm-name "ScheduledTaskErrors" \
  --metric-name Errors \
  --namespace AWS/Lambda \
  --dimensions Name=FunctionName,Value=my-scheduled-task \
  --statistic Sum \
  --period 300 \
  --threshold 1 \
  --comparison-operator GreaterThanOrEqualToThreshold \
  --evaluation-periods 1 \
  --alarm-actions arn:aws:sns:us-east-1:123456789:my-alerts

Production Tips

Timeout: Set your Lambda timeout higher than the expected execution time. The default is 3 seconds — increase it for cron jobs.

Dead letter queue: Configure a DLQ for failed invocations so you don't lose events: