① Before Save

• Load old record; run system validation (required, type, length)
• Before-save record-triggered flows
• Before triggers
• System validation again + custom validation rules
• Duplicate rules (block → stop)

② Save

• Record written to DB — not committed

③ After Save

• After triggers
• Assignment → auto-response → workflow → escalation
• Workflow field update → update triggers fire once more
• Processes (PB) → after-save flows
• Roll-up / cross-object → parent re-saves
• Criteria-based sharing recalc

④ Commit → Post-commit

• Commit all DML → send email → async Apex

Use BEFORE for…

• Validation
• Setting/defaulting fields on the same record (no DML)
• Blocking with addError()
• Note: before insert has no record Id yet

Use AFTER for…

• Anything needing the record Id
• Creating child/related records
• Roll-ups, email, async callouts
• Trigger.new is read-only here

Relationship queries

• Child→Parent (up): Account.Name; custom Custom__r.Name
• Parent→Child (down): subquery (SELECT LastName FROM Contacts); custom Line_Items__r
• Aggregates → AggregateResult[], ar.get('alias'), GROUP BY
• SOSL = text search across objects → List<List<sObject>>

DML partial success & errors

• insert list; = all-or-none (throws DmlException)
• Database.insert(list, false) = partial → SaveResult[] → isSuccess()/getErrors()
• Custom exception must end in Exception and extend Exception
• addError() in a trigger blocks DML with a user error

Platform

• MVC: Model = objects/DB · View = VF/LWC/layouts · Controller = Apex
• Multitenancy → shared infra → why governor limits exist
• Declarative first; Apex only when too complex / high bulk / callout parsing / transactional control

Data & deployment

• Import: Wizard ≤50k (dedupe) · Data Loader >50k
• Change Sets = related orgs, metadata only (no records)
• SFDX + CLI + VS Code = modern tooling (replaced Force.com IDE)
• Debug levels: ERROR < WARN < INFO < DEBUG < FINE < FINER < FINEST

Test: startTest / stopTest + bulk

@isTest private class AcctTest {
  @testSetup static void seed() { insert new Account(Name='Seed'); }
  @isTest static void bulk() {
    List<Account> a = new List<Account>();
    for (Integer i=0;i<200;i++) a.add(new Account(Name='A'+i));
    Test.startTest();  insert a;  Test.stopTest();
    System.assertEquals(201, [SELECT COUNT() FROM Account]);
  }
}

HttpCalloutMock

@isTest global class MyMock implements HttpCalloutMock {
  global HttpResponse respond(HttpRequest req) {
    HttpResponse res = new HttpResponse();
    res.setStatusCode(200);
    res.setBody('{"ok":true}');
    return res;
  }
}
// Test.setMock(HttpCalloutMock.class, new MyMock());

Queueable (chainable)

public class MyJob implements Queueable,
                              Database.AllowsCallouts {
  public void execute(QueueableContext c) {
    // work...
    if (more) System.enqueueJob(new MyJob()); // chain
  }
}
// System.enqueueJob(new MyJob()); -> Job Id

Batch skeleton

public class MyBatch implements
    Database.Batchable<sObject>, Database.Stateful {
  public Database.QueryLocator start(Database.BatchableContext bc){
    return Database.getQueryLocator('SELECT Id FROM Account');
  }
  public void execute(Database.BatchableContext bc,
                      List<sObject> scope){ /* fresh limits */ }
  public void finish(Database.BatchableContext bc){ /* email */ }
}
// Database.executeBatch(new MyBatch(), 200);

Pacing & triage

• Two-pass: answer knowns, flag code-tracing, return later (~90s/Q)
• Read the last line first on long stems
• Never let one question eat 5 minutes

Answering

• Multi-select = all-or-nothing — obey "choose two/three"
• Eliminate obvious wrongs first
• "bulkified / efficient / governor-safe" → the no-SOQL-in-loop answer
• Slow down on home-turf topics; trust first instinct