Declarative Automation and Combining Flow with Apex

What it is

Flow is Salesforce's declarative automation tool. Workflow Rules and Process Builder reached end of support on 31 December 2025; existing ones still run, but new automation is built in Flow or Apex.

A developer must know what Flow can do on its own, and how to extend it with Apex when it cannot: an invocable method lets a flow call Apex, and Apex can start a flow.

How it works

Flow types

Record-triggered flows run before save (fast field updates on the triggering record) or after save (related records, actions, email). They can also have scheduled paths and a run asynchronously path.

When Flow is not enough

Invocable methods: Flow calls Apex

public with sharing class TierLookup {
    public class Request {
        @InvocableVariable(required=true label='Contact Id')
        public Id contactId;
    }
    public class Result {
        @InvocableVariable public String tier;
    }
    @InvocableMethod(label='Get Tier' description='Returns the loyalty tier for each contact')
    public static List<Result> run(List<Request> requests) {
        Set<Id> ids = new Set<Id>();
        for (Request r : requests) ids.add(r.contactId);
        Map<Id, Contact> byId = new Map<Id, Contact>(
            [SELECT Tier__c FROM Contact WHERE Id IN :ids]);
        List<Result> out = new List<Result>();
        for (Request r : requests) {
            Result res = new Result();
            res.tier = byId.containsKey(r.contactId) ? byId.get(r.contactId).Tier__c : null;
            out.add(res);
        }
        return out;
    }
}

Rules for @InvocableMethod:

• Static, and public or global.
• Only one invocable method per class.
• Takes at most one parameter, a List (of primitives, sObjects or a class with @InvocableVariable fields), and returns a List or nothing.
• When a record-triggered flow runs for 200 records, the method is called once with a list of 200 inputs. Return one output per input, in the same order.

The same invocable method can be used as an Agentforce agent action; its label and descriptions help the agent choose it and fill its inputs.

Apex starts a flow

Map<String, Object> inputs = new Map<String, Object>{ 'recordId' => acc.Id };
Flow.Interview interview = Flow.Interview.createInterview('Welcome_Pack', inputs);
interview.start();

Platform events connect both sides

Publish an event from Apex with EventBus.publish(event) or from Flow with a Create Records element. Subscribe with an Apex trigger (after insert on the event) or a platform event-triggered flow. Platform event triggers run as the Automated Process user by default.

A worked example

A record-triggered flow on Opportunity must assign a risk score that needs a weighted calculation across related records. The admin keeps the flow, and the developer writes an invocable method that accepts a list of Opportunity Ids, queries everything once, and returns the scores in input order. The flow calls it as an Apex action, then sets the field. Admins keep control of the process; the hard logic stays bulk-safe in Apex.

How the exam asks about this

• "Make an Apex method available to Flow." @InvocableMethod.
• "Expose fields of an input class to Flow." @InvocableVariable.
• "How many times is the invocable method called for 200 records?" Once, with a list of 200.