TechAim – Salesforce Developer Interview Questions​

Quick answers to key questions

• LWC decorators. @api makes a property or method public so a parent component can use it. @track makes changes inside objects and arrays reactive (simple fields are reactive by default in current versions). @wire connects a property or function to a data source such as Apex or the Lightning Data Service.
• Why AuraEnabled? It exposes an Apex method to Lightning components. Use cacheable=true for read-only methods used with @wire.
• How many records can a SOQL query return? A transaction can retrieve up to 50,000 records in total across all its SOQL queries. A batch Apex query locator can go up to 50 million records.
• Asynchronous Apex. Future methods, queueable Apex, batch Apex and scheduled Apex. They run in the background, with higher limits than synchronous code.
• Use of the finish method in batch Apex. It runs once after all batches are done. Use it for post-processing, such as sending a summary email or starting another batch job.
• Exception handling in a future method. A future method returns nothing, and the caller cannot catch its errors. Use try and catch inside the method and log the error in a custom object or send an email.
• Role, profile and permission set. A role decides which records a user can see through the hierarchy. A profile sets the base object, field and system permissions. A permission set adds extra permissions to a user.
• Configuration for API integration. Enable API access for the integration user, create a Connected App for OAuth, store the endpoint and credentials in a Named Credential, and give the integration user only the permissions it needs. Check IP restrictions and the authentication flow as well.
• Types of reports and dashboards. Reports can be tabular, summary, matrix or joined. Dashboards show charts, gauges, metrics and tables built from reports.
• Authentication and authorization. Authentication proves who you are, for example with a username, password and MFA. Authorization decides what you are allowed to do after you are logged in.

Throw an error if the Account already has a Contact

trigger ContactTrigger on Contact (before insert) {
    Set<Id> accountIds = new Set<Id>();
    for (Contact c : Trigger.new) {
        if (c.AccountId != null) accountIds.add(c.AccountId);
    }
    Set<Id> accountsWithContact = new Set<Id>();
    for (Contact existing : [SELECT AccountId FROM Contact WHERE AccountId IN :accountIds]) {
        accountsWithContact.add(existing.AccountId);
    }
    for (Contact c : Trigger.new) {
        if (c.AccountId != null && accountsWithContact.contains(c.AccountId)) {
            c.addError('This Account already has a Contact.');
        }
    }
}

If more than one new Contact for the same Account is inserted in one batch, add a check that also tracks the Accounts seen in the current batch.