Apex CPU time limit exceeded.

// ❌ BAD: Nested loops with O(n²) complexity
// Works fine with 100 records in Sandbox
// Burns through CPU time with 10,000+ records in Production

public void calculateCommission(List<Opportunity> opps) {
    for (Opportunity opp1 : opps) {
        for (Opportunity opp2 : opps) {
            // O(n²) comparison - exponential CPU growth
            if (opp1.AccountId == opp2.AccountId) {
                Decimal commission = calculateComplexFormula(opp1, opp2);
                opp1.Commission__c = commission;
            }
        }
    }
    update opps;
}
// With 10,000 opportunities = 100,000,000 iterations
// CPU timeout at 10 seconds

// ✅ GOOD: Use Maps for O(n) complexity
// Linear time regardless of record count

public void calculateCommission(List<Opportunity> opps) {
    // Group by AccountId using a Map
    Map<Id, List<Opportunity>> oppsByAccount = new Map<Id, List<Opportunity>>();
    
    for (Opportunity opp : opps) {
        if (!oppsByAccount.containsKey(opp.AccountId)) {
            oppsByAccount.put(opp.AccountId, new List<Opportunity>());
        }
        oppsByAccount.get(opp.AccountId).add(opp);
    }
    
    // Process each account's opportunities
    for (List<Opportunity> accountOpps : oppsByAccount.values()) {
        for (Integer i = 0; i < accountOpps.size(); i++) {
            Decimal commission = calculateFormula(accountOpps[i]);
            accountOpps[i].Commission__c = commission;
        }
    }
    update opps;
}