Batch Apex Practice Problems

Problem Statement

Build a Database.Batchable class that finds and merges duplicate Lead records sharing the same email address.

Keep the most recently created record and merge others into it. Log results to a custom object Merge_Log__c.

Requirements

• Batch size: 200 records
• Use Database.merge() for the actual merging
• The finish() method must send a summary email

Problem Statement

Write a Batch Apex class that archives closed Opportunities older than a given number of days.

Requirements:

• Implement Database.Batchable<SObject> interface
• Constructor accepts Integer daysOld (archive opps closed more than this many days ago)
• start(): return a Database.QueryLocator for Opportunities where StageName IN ('Closed Won','Closed Lost') AND CloseDate < :cutoffDate
• execute(): set Archived__c = true on each record in the batch and update
• finish(): send an email to the running user with the batch completion summary
• Also implement Database.Stateful to track total records processed across batches

Constraints

• Use Database.update(scope, false) for partial success
• Track failed record count using a stateful instance variable

Problem Statement

1,000 Account records are processed by a Batch Apex job that updates a custom field Last_Processed__c (DateTime). Some records may fail (e.g., validation rules, locked records).

Write the batch class so it:

• Uses Database.update(records, false) (partial success) instead of the all-or-nothing DML.
• Collects each failed record's Id and error message into a custom object Batch_Error_Log__c with fields Record_Id__c and Error_Message__c.
• In finish(), sends an email summarising total records processed and failures.

Best Practices

• Batch size: 200.
• Do NOT re-throw exceptions — log them instead.
• Test with Database.executeBatch() inside Test.startTest()/stopTest().

Problem Statement

Write a Batch Apex class AccountRevenueTierBatch that reads every Account and sets a custom field Revenue_Tier__c based on AnnualRevenue:

• Enterprise — AnnualRevenue ≥ 1,000,000
• Medium — AnnualRevenue 100,000 – 999,999
• Small — AnnualRevenue < 100,000 or null

Requirements

• Implement Database.Batchable<SObject> with all three methods.
• start(): query Id, AnnualRevenue, Revenue_Tier__c FROM Account.
• execute(): assign tier, skip records where value did not change, call Database.update(list, false) outside the loop.
• finish(): log completion with System.debug.

Best Practices

• Treat null AnnualRevenue as 0 — never call arithmetic on null.
• Guard DML: if (!toUpdate.isEmpty()) before updating.
• Database.update(list, false) allows partial success — safe for bulk runs.
• Never place SOQL or DML inside a loop.

Problem Statement

Write StaleContactDeactivationBatch that marks Contacts as stale when they have had no activity for 24 months.

Requirements

• Implement Database.Batchable<SObject> and Database.Stateful.
• Declare instance variables processedCount and failedCount (both Integer, both global).
• start(): filter Contacts where Is_Stale__c = false AND (LastActivityDate < 24 months ago OR LastActivityDate = null).
• execute(): set Is_Stale__c = true, call Database.update(list, false), iterate SaveResult to count successes and failures, log each error with System.debug.
• finish(): log both counts.

Best Practices

• Use Database.Stateful to accumulate counts across batches.
• Inspect every Database.SaveResult — never silently swallow errors.
• Cutoff date: Date.today().addMonths(-24).

Problem Statement

Write ContactTitleSyncBatch that reads all Contacts with an Account and sets the Contact's Title field based on the parent Account's Industry.

Industry → Title Mapping

• Technology → 'Technology Professional'
• Finance → 'Finance Professional'
• Healthcare → 'Healthcare Professional'
• Any other → 'Industry Professional'

Requirements

• Implement Database.Batchable<SObject>.
• start(): query Id, Title, Account.Industry FROM Contact WHERE AccountId != null (child-to-parent).
• execute(): skip Contacts with null Industry; only update when title changes; wrap DML in try-catch(DmlException e).
• finish(): log with System.debug.

Best Practices

• Use child-to-parent SOQL (Account.Industry) — avoids a second query.
• Skip null industry with continue — defensive coding.
• Wrap DML in try-catch to log errors without aborting the batch.
• Only add records to the update list when the value actually changes.

Problem Statement

Write AccountEngagementScoreBatch that calculates a custom Engagement_Score__c for every Account using three signals, and logs all errors via Database.Stateful.

Scoring Rules

• +40 if AnnualRevenue ≥ 1,000,000
• +30 if NumberOfEmployees ≥ 100
• +30 if Account has at least one Contact (use a subquery)

Requirements

• Implement Database.Batchable<SObject> and Database.Stateful.
• Declare: global Integer successCount, global Integer errorCount, global List<String> errorLog.
• start(): include a parent-to-child subquery (SELECT Id FROM Contacts LIMIT 1).
• execute(): wrap per-record scoring in try-catch(Exception e); call Database.update(list, false); inspect every Database.SaveResult.
• finish(): log counts and every entry in errorLog.

Problem Statement

Write a batch class StaleOpportunityBatch that marks all Prospecting Opportunities that were created more than 365 days ago as Closed Lost.

Requirements

1. Implement Database.Batchable<SObject>.
2. start() — return a Database.QueryLocator for Opportunities WHERE StageName = 'Prospecting', IsClosed = false, CreatedDate <= :cutoff (cutoff = today minus 365 days).
3. execute() — set StageName = 'Closed Lost' and CloseDate = Date.today(); save with Database.update(scope, false).
4. finish() — log the job Id with System.debug.

Best Practices

• Use Database.getQueryLocator() — not a List — so Salesforce paginates up to 50M rows.
• Guard execute() with scope.isEmpty().
• Database.update(scope, false) — partial saves: one bad record does not roll back the chunk.

Problem Statement

Write LeadScoreResetBatch that implements both Database.Batchable<SObject> and Database.Stateful. It resets Lead_Score__c to 0 on all unconverted Leads and tracks how many records succeeded and failed across all chunks.

Requirements

1. Implement both Database.Batchable<SObject> and Database.Stateful.
2. Declare private Integer processedCount = 0 and private Integer failedCount = 0 as instance variables.
3. start() — query unconverted Leads with Lead_Score__c > 0.
4. execute() — reset Lead_Score__c = 0, save with Database.update(scope, false), inspect Database.SaveResult[] to increment counters.
5. finish() — log the totals.

Key Concept: Database.Stateful

Without Database.Stateful, instance variables are reset to their defaults between each execute() call. With it, they persist across all chunks — essential for aggregating results.

Problem Statement

Write ContactEmailDomainBatch that enforces an allowed email domain (salesforce.com) across all Contacts. Contacts with non-compliant emails should have their Email field cleared. Use partial DML and capture errors.

Requirements

1. Implement Database.Batchable<SObject> and Database.Stateful.
2. Declare constants/fields: ALLOWED_DOMAIN, errorLog, successCount.
3. start() — query Contacts WHERE Email != null.
4. execute() — for each Contact, if email doesn't end with @salesforce.com, set Email = null and add to update list. Use Database.update(toUpdate, false) and inspect SaveResult[].
5. finish() — log success count and all error messages.

Best Practices

• Use a local toUpdate list — don't update all scope records, only those that changed.
• Guard with toUpdate.isEmpty() before DML — avoids unnecessary governor usage.
• Use indexed access results[i] alongside toUpdate[i] to correlate errors back to the correct record Id.

Problem Statement

Write AccountAddressSyncBatch that copies each Account's billing address to all of its child Contacts' mailing address fields in bulk.

Requirements

1. Implement Database.Batchable<SObject>.
2. start() — query Accounts WHERE BillingCity != null.
3. execute():
   • Collect Account Ids from the scope batch.
   • Build a Map<Id, Account> from scope for O(1) lookup.
   • Query all child Contacts in one SOQL: WHERE AccountId IN :accountIds.
   • Copy BillingCity → MailingCity, BillingState → MailingState, BillingPostalCode → MailingPostalCode, BillingCountry → MailingCountry.
   • Bulk update with Database.update(toUpdate, false).

Key Challenge

A SOQL inside execute() is allowed (one per chunk) — but it must be outside any loop. Build the Id set first, then query once.

Problem Statement

Implement two chained batch classes:

1. RevenueRollupBatch — calculates total closed-won revenue per Account (using a parent-child subquery), writes it to Total_Closed_Won_Revenue__c, then chains AccountTierAssignmentBatch in finish().
2. AccountTierAssignmentBatch — assigns Account_Tier__c (Platinum/Gold/Silver/Bronze) based on the revenue field.

Chaining Rules

• Guard chain in finish() with if (!Test.isRunningTest()) — you cannot enqueue from inside a batch during test execution.
• RevenueRollupBatch must be Database.Stateful to count processed Accounts across chunks.
• Skip records where the tier has not changed — only DML when needed.

Problem Statement

Write WeeklyOpportunityCleanupScheduler that implements Schedulable and kicks off StaleOpportunityBatch on a scheduled basis.

Requirements

• Implements Schedulable.
• Declare a @TestVisible private Integer batchSize = 200 field.
• execute(SchedulableContext sc) — creates a new StaleOpportunityBatch() and calls Database.executeBatch(batch, batchSize).

How to Schedule

String cron = '0 0 2 ? * MON *'; // Every Monday at 2 AM
String jobName = 'Weekly Opp Cleanup';
System.schedule(jobName, cron, new WeeklyOpportunityCleanupScheduler());

Best Practices

• Store batch size in an @TestVisible field so tests can override it.
• Keep execute() minimal — one line to create and enqueue the batch.
• Salesforce CRON: Seconds Minutes Hours Day Month DayOfWeek Year.

Problem Statement

Write MonthlyLeadSummaryScheduler that implements Schedulable and emails a monthly report of new unconverted Leads to an admin.

Requirements

1. Implements Schedulable.
2. @TestVisible private String recipientEmail = 'admin@salesforce.com'.
3. execute(SchedulableContext sc):
   • Query COUNT() of Leads WHERE IsConverted = false AND CreatedDate = THIS_MONTH.
   • Build a Messaging.SingleEmailMessage with subject and body.
   • Send via Messaging.sendEmail() guarded by !Test.isRunningTest().

Best Practices

• Guard Messaging.sendEmail() with !Test.isRunningTest() — sending email in tests uses the daily email allowance.
• Use the THIS_MONTH date literal — cleaner than calculating start/end dates.
• Store the recipient in a @TestVisible field for testability.

Problem Statement

Write HourlyDataMonitorScheduler that runs every hour, counts new open Cases, alerts on spikes, and re-schedules itself for the next hour automatically.

Requirements

1. Implements Schedulable.
2. private static final String JOB_NAME = 'HourlyDataMonitor'.
3. @TestVisible private static String buildNextHourCron() — builds a CRON expression for exactly one hour from now using DateTime.now().addHours(1) and String.format().
4. execute():
   • Count Cases created in the last hour: CreatedDate >= :oneHourAgo.
   • Log count. If count > 50, log an alert.
   • Abort current job with System.abortJob(sc.getTriggerId()).
   • Re-schedule with System.schedule(JOB_NAME, buildNextHourCron(), new HourlyDataMonitorScheduler()).
   • Guard all scheduling code with !Test.isRunningTest().

Self-Rescheduling Pattern

Salesforce Scheduled Jobs run once. To simulate a recurring job at intervals shorter than 1 day (which standard Apex Scheduling via UI cannot express), the job re-schedules itself in execute(). Always abort the current job first to avoid duplicate schedules building up.