Overview
In Salesforce, Governor Limits are crucial because they ensure that all customers on the multi-tenant platform have equitable access to shared resources. Understanding and optimizing code within these limits is essential for developing scalable and efficient applications on Salesforce.
Key Concepts
- Multi-Tenant Architecture: Salesforce uses a multi-tenant architecture where multiple customers share common resources. Governor limits are enforced to prevent any single customer from monopolizing shared resources.
- Types of Governor Limits: There are various types of Governor Limits in Salesforce, including but not limited to SOQL queries, DML operations, and CPU time.
- Best Practices for Optimization: Adopting best practices to work within these limits, such as bulkifying code, efficient query writing, and using asynchronous processes, is key to optimizing performance.
Common Interview Questions
Basic Level
- What are Governor Limits in Salesforce?
- Can you give examples of three common Governor Limits?
Intermediate Level
- How do SOQL query limits work and how can you optimize queries to stay within these limits?
Advanced Level
- Describe a scenario where you had to optimize a batch Apex job to comply with Governor Limits. What strategies did you employ?
Detailed Answers
1. What are Governor Limits in Salesforce?
Answer: Governor Limits in Salesforce are runtime limits enforced by the Apex runtime engine to prevent individual Apex code from monopolizing shared resources on the multi-tenant platform. These limits ensure efficient and fair use of resources among all Salesforce customers.
Key Points:
- Ensure fair usage among customers.
- Prevent monopolization of shared resources.
- Enforced at runtime by the Apex engine.
Example:
// This C# example illustrates the concept in a general programming context
// Imagine a multi-tenant application where you must limit resource usage per tenant
public class TenantResourceManager {
private const int MaxQueries = 100; // Simulate a Governor Limit
private int queryCount = 0;
public bool TryExecuteQuery() {
if (queryCount >= MaxQueries) {
Console.WriteLine("Query limit reached. Please try again later.");
return false;
} else {
queryCount++; // Simulate executing a query
Console.WriteLine("Query executed successfully.");
return true;
}
}
}
2. Can you give examples of three common Governor Limits?
Answer: Yes, common Governor Limits in Salesforce include:
- SOQL queries limit per transaction.
- DML operations limit per transaction.
- Total heap size limit.
Key Points:
- SOQL queries: Limits the number of SOQL queries that can be made.
- DML operations: Limits the number of DML operations (insert, update, delete, etc.) in a transaction.
- Heap size: Limits the total amount of memory allocation in a single transaction.
Example:
// This example is conceptual and demonstrates how you might enforce similar limits in C#
public class ApexTransactionSimulator {
private const int MaxSOQLQueries = 100;
private const int MaxDMLOperations = 150;
private const int MaxHeapSize = 6000000; // in bytes
private int currentSOQLQueries = 0;
private int currentDMLOperations = 0;
private int currentHeapSize = 0;
public bool TryAddSOQLQuery() {
if (currentSOQLQueries >= MaxSOQLQueries) {
Console.WriteLine("SOQL query limit reached.");
return false;
} else {
currentSOQLQueries++;
return true;
}
}
public bool TryAddDMLOperation() {
if (currentDMLOperations >= MaxDMLOperations) {
Console.WriteLine("DML operation limit reached.");
return false;
} else {
currentDMLOperations++;
return true;
}
}
public bool TryAllocateMemory(int size) {
if ((currentHeapSize + size) > MaxHeapSize) {
Console.WriteLine("Heap size limit exceeded.");
return false;
} else {
currentHeapSize += size;
return true;
}
}
}
3. How do SOQL query limits work and how can you optimize queries to stay within these limits?
Answer: SOQL query limits restrict the number of queries that can be executed in a single transaction. To optimize queries and stay within these limits, you can:
- Use bulkified queries to retrieve data for multiple records at once.
- Apply selective filters in SOQL queries to reduce the number of records fetched.
- Use the @ReadOnly annotation for read-only operations to increase limits in certain contexts.
Key Points:
- Bulkify queries to minimize the number of individual queries.
- Use selective SOQL queries to limit data volume.
- Leverage @ReadOnly annotation for higher query limits in read-only contexts.
Example:
// While specific SOQL syntax cannot be demonstrated with C#, the concepts can be explained
// Imagine optimizing database access in a multi-tenant application
public class DataOptimizer {
public void RetrieveBulkData() {
// Instead of:
// foreach (var id in recordIds) {
// var record = database.Query($"SELECT * FROM Records WHERE Id = {id}");
// }
// Use a bulk query approach:
// var records = database.Query($"SELECT * FROM Records WHERE Id IN ({string.Join(",", recordIds)})");
Console.WriteLine("Data retrieved using bulk query approach.");
}
}
4. Describe a scenario where you had to optimize a batch Apex job to comply with Governor Limits. What strategies did you employ?
Answer: In a scenario where a batch Apex job was processing thousands of records and hitting the SOQL query limit, several strategies were employed to optimize:
- Bulkification: Combined multiple operations into single batch jobs to reduce the number of transactions.
- Efficient Query Design: Ensured SOQL queries were selective and only retrieved necessary fields.
- Stateless Batches: Avoided storing state between batches to minimize heap size usage.
Key Points:
- Bulkification reduces the number of transactions.
- Selective querying minimizes data retrieval and processing time.
- Stateless design helps stay within heap size limits.
Example:
// Conceptual demonstration with C#, focusing on efficient processing strategies
public class BatchProcessor {
public void ProcessRecords(IEnumerable<Record> records) {
// Assuming each "Record" has been efficiently queried and minimized in size
foreach (var batch in SplitIntoBatches(records, 200)) { // Simulate batch processing
foreach (var record in batch) {
// Process each record without exceeding governor limits
}
// Assume here we perform an operation that could potentially hit governor limits
Console.WriteLine("Processed a batch without hitting governor limits.");
}
}
private IEnumerable<IEnumerable<T>> SplitIntoBatches<T>(IEnumerable<T> items, int batchSize) {
// Logic to split items into batches of specified size
return new List<List<T>>(); // Placeholder return
}
}
