Understanding Apex's Execution Environment

Governor Limits

Governor limits are enforced to ensure no single tenant monopolizes shared resources. Common culprits include too many SOQL queries, DML statements, or CPU time per transaction. These limits vary between synchronous and asynchronous contexts.

Trigger Lifecycle and Recursion

Triggers execute in specific contexts (before insert, after update, etc.). Improperly managed recursion or chained DML can inadvertently cause infinite loops or partial updates. Enterprise orgs with layered automation—flows, workflows, Apex, and managed packages—are especially prone to cascading effects.

Diagnosing Complex Apex Issues

1. Too Many SOQL Queries

This often results from queries inside loops. Even indirect method calls or utility classes can cause this pattern unintentionally.

for (Account acc : accList) {
  List contacts = [SELECT Id FROM Contact WHERE AccountId = :acc.Id];
}

Fix by bulkifying the logic:

Map> contactMap = new Map>();
for (Contact c : [SELECT Id, AccountId FROM Contact WHERE AccountId IN :accIds]) {
  if (!contactMap.containsKey(c.AccountId)) {
    contactMap.put(c.AccountId, new List());
  }
  contactMap.get(c.AccountId).add(c);
}

2. Mixed DML Errors

This occurs when standard and setup objects (e.g., User, Group) are modified in the same transaction. Salesforce prohibits this in synchronous contexts.

User u = [SELECT Id FROM User WHERE Username = This email address is being protected from spambots. You need JavaScript enabled to view it.'];
Account a = new Account(Name = 'Acme');
insert u; insert a; // Causes MIXED_DML_OPERATION error

Resolve by moving setup object logic into a future method:

@future
public static void insertUserAsync(User u) {
  insert u;
}

3. CPU Time Limit Exceeded

This is common in recursive triggers, deeply nested loops, or inefficient string manipulations. Use limits.getCpuTime() to profile long-running sections.

Integer start = Limits.getCpuTime();
// logic here
System.debug('CPU Used: ' + (Limits.getCpuTime() - start));

4. Trigger Order and Unintended Side Effects

When multiple triggers or automation mechanisms run on the same object, unpredictable ordering can cause missed updates or conflicting DML.

Use trigger handler frameworks to control execution explicitly:

TriggerHandler.run(new AccountTriggerHandler(), Trigger.new, Trigger.old, Trigger.isInsert);

Advanced Troubleshooting and Tools

Debug Logs and Execution Trees

Use filtered debug logs with log levels set to FINER or FINEST to inspect variable values and limits. Look for cumulative sections to identify patterns.

Checkpoints and Heap Dumps

In Developer Console, set checkpoints to capture object state. Useful for identifying memory leaks or unexpected null values in deep call chains.

Automated Testing for Governor Boundaries

Write test methods that simulate high-load scenarios. Use Test.startTest() and Test.stopTest() to measure governor consumption accurately.

@isTest
static void testBulkInsert() {
  List accounts = new List();
  for (Integer i = 0; i < 200; i++) {
    accounts.add(new Account(Name='Test Acc ' + i));
  }
  Test.startTest();
  insert accounts;
  Test.stopTest();
}

Best Practices for Large-Scale Apex Development

• Bulkify all DML and SOQL logic
• Isolate automation logic into service or trigger handler classes
• Use Custom Settings or Custom Metadata to enable/disable logic dynamically
• Leverage Platform Events for decoupled async processing
• Test governor limits with realistic data volumes

Conclusion

Developing scalable and reliable Apex code in enterprise Salesforce orgs requires deep familiarity with the platform's execution model. From governor limits to multi-trigger chaos, most advanced issues can be mitigated through strict bulkification, asynchronous isolation, and layered architecture. With the right tools and defensive coding strategies, teams can ensure high-performing Apex logic that aligns with Salesforce's best practices.

FAQs

1. Why do I get a MIXED_DML_OPERATION error in Apex?

You're performing DML on setup and non-setup objects in the same transaction. Use @future methods to separate them.

2. How can I prevent Apex CPU time limit errors?

Refactor recursive logic, avoid unnecessary loops, and profile performance with Limits.getCpuTime().

3. What's the best way to control trigger execution order?

Use a trigger framework that defines execution phases and ensures deterministic behavior for multi-trigger scenarios.

4. Can I test governor limits in unit tests?

Yes. Use Test.startTest() and Test.stopTest() to simulate real execution contexts and track limit consumption.

5. What tools help debug complex Apex transactions?

Use debug logs with FINER settings, checkpoints in Developer Console, and the Salesforce CLI for asynchronous log retrieval.