Free Sample Lesson: Choosing asynchronous Apex (Platform Developer II Cert Lab)

Free sample lesson from the Platform Developer II Cert Lab. The full course has 22 lessons and 4 full practice exams.

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Process Automation, Logic, and Integration · PL4 · part of the 27% section · about 20 min with practice

PL4: Choosing asynchronous Apex

You’ll be able to: pick future, queueable, batch or scheduled Apex for a requirement and explain the trade-offs.

Which async tool when

Need	Best fit	Key limit or behavior
Callout or long work after a trigger, with simple inputs	Queueable (or future)	Future takes primitives only
Pass sObjects, get a job ID, or chain jobs	Queueable	50 enqueueJob calls per sync transaction; 1 child per parent job
Process millions of records	Batch Apex	QueryLocator up to 50 million records; limits reset per chunk
Run at a set time	Scheduled Apex	Up to 100 scheduled jobs at once
Avoid a mixed DML error	Future or queueable	Separates setup and non-setup DML

Queueable first

Salesforce recommends Queueable Apex instead of future methods. Queueables cover the same use cases and add a job ID from System.enqueueJob (an AsyncApexJob record), non-primitive member variables such as sObjects, and chaining. Future methods take only primitives or collections of primitives, because an sObject could change between the call and the run.

SyncJob.apex

1public class SyncJob implements Queueable, Database.AllowsCallouts {
2    List<Account> accts;
3    public SyncJob(List<Account> a) { accts = a; }
4    public void execute(QueueableContext ctx) {
5        // callout and DML here
6    }
7}

Batch and schedule

Batch Apex runs start, execute and finish. Each execute chunk is its own transaction with fresh limits, and a failed chunk doesn’t roll back earlier ones. Instance variables keep values across chunks only if the class implements Database.Stateful; static variables always reset. Scheduled Apex runs a class on a CRON schedule, ideal for kicking off a nightly batch, and an org can have 100 scheduled jobs at once.

Exam trap

A batch job with scope 200 over 1,000 records is five transactions. If the third fails, the first two stay committed. Design for that partial success.

Predict, then reveal

A trigger must call an external tax service and save the result back to each Opportunity, passing the Opportunity records themselves. Future or queueable?

Show the answer

Queueable with Database.AllowsCallouts: it accepts sObjects and gives you a job ID to monitor.

Try it 5 min · your free Developer Edition org or Trailhead Playground

Write a Queueable that updates a field on 5 accounts.
Enqueue it in anonymous Apex and keep the returned ID.
Query AsyncApexJob for that ID and watch Status move to Completed.

Practice questions

Ten exam-style questions on this lesson. Answer each one before you open it.

Question 1. Which async option does Salesforce recommend over future methods?

A. Queueable Apex
B. Batch Apex
C. Scheduled Apex
D. Platform event triggers

Show the answer and explanation

Answer: A. Salesforce recommends Queueable Apex instead of future methods.

Queueables add job IDs, complex types and chaining.

Question 2. Why can’t a future method accept an Account parameter?

A. Only Strings are allowed
B. Account records are too large for the async heap limit
C. Future methods can’t do DML
D. The record could change before it runs

Show the answer and explanation

Answer: D. sObjects can’t be passed because they may change between the call and the run.

Pass IDs and query inside.

Question 3. What does System.enqueueJob return?

A. A Boolean
B. The AsyncApexJob ID
C. The QueueableContext
D. Nothing

Show the answer and explanation

Answer: B. enqueueJob returns the ID of the AsyncApexJob record.

Use it to monitor the job.

Question 4. How many child jobs can a queueable job chain from its execute method?

A. Unlimited
B. One
C. Five
D. Fifty

Show the answer and explanation

Answer: B. Only one child job can exist for each parent job.

Fifty is the enqueue limit for a synchronous transaction.

Question 5. How many queueable jobs can a synchronous transaction add with System.enqueueJob?

A. 100
B. 200
C. 1
D. 50

Show the answer and explanation

Answer: D. The synchronous limit is 50; the asynchronous limit is 1.

100 is the SOQL limit.

Question 6. A batch job processes 1,000 records with a scope of 200 and the second chunk fails. What happens to the first chunk’s updates?

A. They’re moved to finish()
B. They roll back
C. They stay committed
D. They’re retried

Show the answer and explanation

Answer: C. Each chunk is its own transaction; earlier successful chunks aren’t rolled back.

Design for partial success.

Question 7. A batch class counts processed records across chunks in an instance variable, but the total is always zero in finish(). What’s missing?

A. Database.AllowsCallouts
B. A static variable
C. Database.Stateful
D. Schedulable

Show the answer and explanation

Answer: C. Only with Database.Stateful do instance variables keep values between transactions.

Static variables reset between transactions.

Question 8. How many records can a batch start method return with a QueryLocator?

A. Up to 50 million
B. Up to 50,000 per transaction
C. Up to 10,000
D. Up to 2,000

Show the answer and explanation

Answer: A. A QueryLocator lets batch Apex query up to 50 million records.

50,000 is the normal SOQL row limit.

Question 9. Which statements about scheduled Apex are true? (Choose 2.)

A. It always runs exactly to the second you specify
B. An org can have 100 scheduled jobs at once
C. It can’t start batch jobs
D. Actual run time can be delayed

Show the answer and explanation

Answer: B, D. There’s a 100-job limit and execution can be delayed by service availability.

It’s ideal for kicking off batch jobs.

Question 10. Which are listed uses for future methods? (Choose 2.)

A. Callouts to external web services
B. Chaining jobs with IDs
C. Avoiding the mixed DML error
D. Processing 50 million records with a QueryLocator

Show the answer and explanation

Answer: A, C. Future methods suit callouts and separating DML to bypass the mixed save error.

Chaining is queueable; huge volumes are batch.

Before you move on

1. Which keyword locks rows?

Show answer

FOR UPDATE, without ORDER BY.

2. How many fields can GROUP BY ROLLUP take?

Show answer

Up to three.

Key takeaways

Prefer Queueable over future.
Future takes primitives only.
Batch chunks commit independently; use Database.Stateful for totals.
100 scheduled jobs at once.

Sources

Checked against Salesforce Help, Salesforce Developers docs and Trailhead on Oct 23, 2026. Questions follow the current Platform Developer II exam guide.

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