Quick answers to key questions

Flow and Apex

• Call a flow from Apex. Start an autolaunched flow with the Flow.Interview class.

Map<String, Object> inputs = new Map<String, Object>();
inputs.put('accountId', acc.Id);
Flow.Interview.My_Autolaunched_Flow myFlow = new Flow.Interview.My_Autolaunched_Flow(inputs);
myFlow.start();

• Call Apex from a flow. Use an Apex action that calls an @InvocableMethod. Only one invocable method is allowed in each Apex class.
• Types of flow. Screen, record-triggered, schedule-triggered, platform event-triggered and autolaunched flows.

Lightning Web Components

• Lifecycle order with one parent and two children. The parent constructor runs first, then the parent connectedCallback. Next, the first child runs its constructor and connectedCallback, then the second child does the same. Rendering then finishes from the inside out: renderedCallback runs for child 1, then child 2, and then for the parent.
• Can a wire method be called inside a JavaScript function? No. A wired method is declarative and the platform calls it. If you need to call Apex from a function, import the method and call it imperatively.
• How do we call a method imperatively? Import the Apex method, call it like a function, and handle the returned promise with then and catch, or with async and await.
• What is a promise? An object that represents the result of an operation that finishes later. It can be pending, fulfilled or rejected. You handle it with then, catch and finally, or await.
• Can we do callouts in JavaScript? Browser calls to other domains are blocked unless the site is added to the Trusted URLs (CSP) settings. The recommended way is to make the callout from Apex and call that Apex method from the component.
• Can we show an LWC on a Visualforce page? Yes, with Lightning Out. Wrap the LWC in an Aura component, put that in an Aura app, and load it on the page.
• What if we write cacheable=false? The method cannot be used with @wire, so it must be called imperatively. In return it can perform DML.
• Can we do DML in a method with cacheable=true? No. Cacheable methods are read-only, and DML throws an error.

Apex, data and integration

• DML limits. 150 DML statements per transaction and 10,000 records processed by DML.
• How many records can we query? 50,000 records in total across the SOQL queries of one transaction.
• Master-detail and lookup. In a master-detail relationship the child depends on the parent, takes its sharing from it, is deleted with it and can have roll-up summaries. A lookup is a loose link with its own owner and sharing.
• Junction object. A custom object with two master-detail relationships that creates a many-to-many relationship.
• REST methods, and PUT and PATCH. GET, POST, PUT, PATCH and DELETE. PUT replaces the whole resource, while PATCH changes only the fields you send.
• Callout limits. 100 callouts per transaction, with a total timeout of 120 seconds. This applies to future methods too, and in batch Apex each execute call is its own transaction with its own 100 callouts.
• Access token and refresh token. An access token is a short-lived credential used to call the API. A refresh token lives longer and is used to get a new access token without asking the user to log in again.
• 15 and 18 digit Ids. A 15 digit Id is case-sensitive. An 18 digit Id adds 3 checksum characters, so it is case-insensitive and safe in tools such as Excel and in integrations. Both work in Salesforce.
• Test coverage. At least 75% overall to deploy to production, but aim for 90% or more with meaningful assertions.

Send a record to a third-party API

HttpRequest req = new HttpRequest();
req.setEndpoint('callout:My_Named_Credential/accounts');
req.setMethod('POST');
req.setHeader('Content-Type', 'application/json');
req.setBody(JSON.serialize(new Map<String, Object>{
    'name' => acc.Name,
    'phone' => acc.Phone
}));
HttpResponse res = new Http().send(req);
System.debug(res.getStatusCode());

For 100 records, send them in one request as a JSON list when the other system allows it. If the API accepts only one record per call, use queueable or batch Apex with a small scope, because a transaction allows only 100 callouts, and a callout cannot be made from a trigger directly.