Which interface is implemented for Queueable class? | CRM Curator

A Queueable Apex class implements the System.Queueable interface. The interface has exactly one method: void execute(QueueableContext context).

The minimum legal Queueable

public class SimpleQueueable implements Queueable {
    public void execute(QueueableContext qc) {
        System.debug('Running queueable job: ' + qc.getJobId());
    }
}

Submit it with System.enqueueJob(new SimpleQueueable()); — that call returns the Id of the resulting AsyncApexJob.

Optional marker interfaces

Depending on what your job needs to do, you can also implement:

Interface	Purpose
`Database.AllowsCallouts`	Required to make HTTP callouts from `execute()`
`Schedulable`	Lets the same class be scheduled via `System.schedule()`
`Finalizer` (separate class)	Run cleanup after the job completes, success or fail

public class CalloutQueueable implements Queueable, Database.AllowsCallouts {
    public void execute(QueueableContext qc) {
        HttpResponse res = new Http().send(buildRequest());
        // ...
    }
    private HttpRequest buildRequest() { return null; }
}

Why Queueable over @future

Typed inputs — constructor can take SObjects, custom Apex classes, lists, maps. Future methods only accept primitives.
Job Id — System.enqueueJob returns an Id you can monitor in AsyncApexJob.
Chaining — call System.enqueueJob from inside execute() to chain another Queueable (up to 5 deep in production, unlimited in tests).
Finalizers — attach a System.Finalizer for post-job cleanup, which future methods can’t do.

Common follow-ups

Full namespace? — System.Queueable. The System namespace is implicit so implements Queueable works without import.
How many can I queue in one transaction? — In a synchronous transaction, up to 50 jobs via enqueueJob. From inside a Queueable, only 1 (the next chained job).

Verified against: Apex Developer Guide — Queueable Apex. Last reviewed 2026-05-17 for Spring ‘26.