Scheduled Apex and Cron Expressions Explained Simply

Scheduled Apex runs an Apex class automatically at times you choose, such as every night at 2 AM or every Monday at 8:30. Nobody needs to click a button. It is how most nightly batch jobs, weekly reports and monthly clean-ups start in Salesforce.

In this post, you will learn the Schedulable interface, how to schedule a job from code or Setup, how to read and write cron expressions, and the rules for callouts and limits. It builds on Batch Apex, Queueable Apex and Asynchronous Apex.

What is Scheduled Apex?

Scheduled Apex is a class that implements the Schedulable interface and its execute method. You register it with a name and a timetable, and Salesforce calls execute at each scheduled time. The job runs as the user who scheduled it.

Think of an alarm clock. You set it once for 6 AM on weekdays, and it rings every morning without you touching it again. A cron expression is the alarm setting, and the Schedulable class is what happens when it rings.

Why Scheduled Apex Matters

Many business tasks follow the calendar, not a user’s click. Here is why Scheduled Apex matters at Bright Path Tutors.

• First, the fee increase batch must run every night at 2 AM.
• Also, tutors need a reminder list every weekday at 8:30.
• Next, old enrolments must be archived on the first day of each month.
• Scheduled jobs run even when nobody is logged in.
• Finally, times and frequency stay in one place, easy to change.

So scheduled jobs turn repeating chores into reliable automation.

How Scheduled Apex Works

Scheduled Apex follows a simple flow. First, you write a class that implements Schedulable. Next, you call System.schedule with a job name, a cron expression and an instance of the class. Then Salesforce stores the schedule as a CronTrigger record and returns its Id. After that, at each matching time, Salesforce queues the job and calls execute when resources are free. Finally, execute does the work, often by starting a Batch or Queueable job.

The Schedulable Interface

A Schedulable class implements one method, execute(SchedulableContext sc). Keep it short. Usually it just starts a batch or a Queueable job.

System.schedule

System.schedule(jobName, cronExpression, job) creates the schedule. The job name must be unique in the org.

Cron Expressions

A Salesforce cron expression has six or seven parts: seconds, minutes, hours, day of month, month, day of week and an optional year. Use ? in either day of month or day of week, because you cannot set both.

Scheduling from Setup

Admins can also schedule a class from Setup > Apex Classes > Schedule Apex. This screen supports weekly or monthly runs at a preferred hour, but not every pattern a cron expression allows.

Callouts

Scheduled Apex cannot make synchronous callouts in execute. So start a Queueable or batch job with Database.AllowsCallouts, or call a @future(callout=true) method.

Limits

An org can have up to 100 scheduled Apex jobs at once, or 5 in Developer Edition. Jobs may start a little late when the server is busy.

Cron Expression Examples

The table below shows common schedules.

Cron expression	Runs
0 0 2 * * ?	Every day at 2:00 AM
0 30 8 ? * MON-FRI	Weekdays at 8:30 AM
0 0 9 1 * ?	First day of each month at 9:00 AM
0 0 18 ? * 6L	Last Friday of each month at 6:00 PM
0 0 0,12 * * ?	Every day at midnight and noon

System.schedule vs the Setup Screen

The table below compares the two ways to schedule a class.

Feature	System.schedule in code	Setup > Schedule Apex
Frequency options	Any cron pattern	Weekly or monthly
Exact minute	Yes	Preferred hour only
Repeatable in deployments	Yes, with a script	Manual clicks
Who uses it	Developers	Admins
Best for	Precise or complex schedules	Simple daily or weekly runs

When to use which depends on precision. Use System.schedule for exact times and complex patterns. Use the Setup screen for simple runs that admins manage.

A Real Scheduled Apex Example

Let’s use Scheduled Apex at Bright Path Tutors to start the fee increase batch every night at 2 AM.

Step 1: The Schedulable Class

public with sharing class NightlyFeeScheduler implements Schedulable {

    public void execute(SchedulableContext sc) {
        // Keep execute light: just start the batch job
        Database.executeBatch(new CourseFeeIncreaseBatch(), 200);
    }
}

The class does one thing: it starts CourseFeeIncreaseBatch from the Batch Apex post. So the heavy work runs in chunks with fresh limits, not inside the scheduler.

Step 2: Schedule It

String cron = '0 0 2 * * ?';   // every day at 2:00 AM
Id cronId = System.schedule('Nightly Fee Increase', cron, new NightlyFeeScheduler());
System.debug('Scheduled job: ' + cronId);

Run this once in anonymous Apex. The cron expression means second 0, minute 0, hour 2, any day of the month, any month, no specific day of the week.

Step 3: Check the Schedule

SELECT Id, CronJobDetail.Name, CronExpression, NextFireTime, State
FROM CronTrigger
WHERE CronJobDetail.Name = 'Nightly Fee Increase'

Here is what the query returns after scheduling.

CronExpression: 0 0 2 * * ?   NextFireTime: 2026-09-11 02:00:00   State: WAITING

You can also see the job in Setup > Scheduled Jobs, where you can delete it.

Step 4: Stop the Job

System.abortJob(cronId);

System.abortJob removes the schedule, so the job stops running. Use it before deleting or heavily changing the class.

Scheduled Apex and Deployments

By default, you cannot deploy changes to a class that has active scheduled jobs. So either abort the jobs first and reschedule after, or turn on the deployment setting that allows changes while Apex jobs are pending.

Common Mistakes with Scheduled Apex

• Putting heavy logic directly in execute instead of starting a batch.
• Making synchronous callouts from execute.
• Setting both day of month and day of week instead of using ?.
• Forgetting the 100 job limit, or 5 in Developer Edition.
• Expecting the job to start at the exact second.

Best Practices for Scheduled Apex

• Keep execute short and start Batch or Queueable jobs from it.
• Give every job a clear, unique name.
• Store cron expressions in custom metadata so admins can change them.
• Check Setup > Scheduled Jobs after each deployment.
• Use System.scheduleBatch for one-time delayed batch runs.

Practice Task

Schedule a job that runs a tutor reminder class every weekday at 8:30 AM. Hint: use the cron expression 0 30 8 ? * MON-FRI and a unique job name.

Most Asked Interview Questions on Scheduled Apex

Scheduling questions are common in practical interviews. Here are the 21 questions asked most about Scheduled Apex.

Basic Questions on Scheduled Apex

Code and Scenario Questions on Scheduled Apex

Advanced Questions on Scheduled Apex

Official Resources

• Apex Scheduler (Apex Developer Guide)
• Schedule Jobs Using the Apex Scheduler (Trailhead)

Quick Recap

• Scheduled Apex runs a Schedulable class at set times.
• System.schedule takes a job name, a cron expression and the job.
• Cron expressions use seconds, minutes, hours, day, month and weekday.
• Keep execute light and start Batch or Queueable work from it.
• An org can have up to 100 scheduled Apex jobs.

What’s Next?

Not every job runs on a clock. Some react to events. Next, read our guide to Salesforce Platform Events in Apex.