Queueable Apex Practice Problems (3) — With Full Explanations

This guide walks through 3 Queueable Apex for chainable, stateful asynchronous processing. Each entry below includes the full problem statement, the governor-limit and best-practice constraints it's testing, and a numbered approach to solving it — then you can open the same problem in ApexArena's browser-based Apex editor and get instant pass/fail feedback against real test cases.

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1. Queueable: Recalculate Opportunity Health Score
2. Queueable: Chained Jobs — Account Tier then Contact Tag
3. Queueable: Mass Opportunity Stage Update with Retry Logic

Medium QueueableAsync Apex

1. Queueable: Recalculate Opportunity Health Score

Problem #210 · Salesforce Apex Coding Challenge

Problem Statement

Write OpportunityHealthScoreQueueable that implements Queueable and recalculates a custom Health_Score__c field on a set of Opportunities.

Scoring Rules

+30 if Amount ≥ 50,000
+20 if CloseDate ≥ today (not in the past)
+25 if StageName is 'Proposal/Price Quote' or 'Value Proposition'
+50 if StageName is 'Closed Won'

Requirements

Implement Queueable.
Constructor accepts Set<Id> opportunityIds.
execute(QueueableContext context): guard empty input, query Opps, compute score, bulk update.

Best Practices

SOQL and DML outside loops.
Guard with isEmpty() before DML.
Enqueue: System.enqueueJob(new OpportunityHealthScoreQueueable(ids));

Approach

1Class signature: public class OpportunityHealthScoreQueueable implements Queueable
2execute() signature: public void execute(QueueableContext context)
3Guard: if (opportunityIds == null || opportunityIds.isEmpty()) return;
4Enqueue from trigger/class: System.enqueueJob(new OpportunityHealthScoreQueueable(myIds));

Hard QueueableAsync Apex

2. Queueable: Chained Jobs — Account Tier then Contact Tag

Problem #211 · Salesforce Apex Coding Challenge

Problem Statement

Implement the chained Queueable pattern with two classes:

AccountTierQueueable — sets Revenue_Tier__c on Accounts, then chains to ContactTagQueueable.
ContactTagQueueable — sets Contact_Segment__c = 'Processed' on related Contacts.

Requirements

Both classes implement Queueable.
Both accept Set<Id> accountIds via constructor.
AccountTierQueueable.execute(): update Revenue_Tier__c per scoring rules, then call System.enqueueJob(new ContactTagQueueable(accountIds)) guarded by !Test.isRunningTest().
ContactTagQueueable.execute(): set Contact_Segment__c = 'Processed' on all Contacts whose AccountId IN :accountIds.

Best Practices

Guard chaining with if (!Test.isRunningTest()) — you cannot enqueue from within a Queueable during test execution without wrapping in Test.startTest()/stopTest().
All SOQL and DML outside loops.

Approach

1Both classes must implement Queueable and have matching constructors.
2Chain with: if (!Test.isRunningTest()) { System.enqueueJob(new ContactTagQueueable(accountIds)); }
3Test.isRunningTest() guard is essential — you cannot enqueue a job from within a Queueable in test context without startTest/stopTest.
4In tests, call ContactTagQueueable directly to test it independently of the chain.

Hard QueueableAsync Apex

3. Queueable: Mass Opportunity Stage Update with Retry Logic

Problem #225 · Salesforce Apex Coding Challenge

Problem Statement

Write OpportunityStageUpdateQueueable that updates a batch of Opportunities to a target StageName. If the DML fails, re-enqueue itself up to MAX_RETRIES = 3 times.

Requirements

Implement Queueable.
Constructor: (List<Id> opportunityIds, String targetStage, Integer retryCount).
Declare private static final Integer MAX_RETRIES = 3.
execute(): guard empty input and blank stage; skip records already at the target stage; wrap DML in try-catch; on failure re-enqueue if retryCount < MAX_RETRIES guarded by !Test.isRunningTest().

Best Practices

Skip records that are already at the target stage — avoids unnecessary DML.
Log the attempt number in the error message for debugging.
Re-enqueue with retryCount + 1 — never modify the field directly before the retry call.

Approach

1Null-safe retryCount in constructor: this.retryCount = retryCount != null ? retryCount : 0;
2Guard blank stage: if (String.isBlank(targetStage)) return;
3Skip already-correct records: if (opp.StageName != targetStage) { ... toUpdate.add(opp); }
4Re-enqueue: System.enqueueJob(new OpportunityStageUpdateQueueable(opportunityIds, targetStage, retryCount + 1));

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