Implement Salesforce Queueable Apex to chain asynchronous jobs with passing state between links in the chain

In-depth guide

Steps

1. Create a class implementing the Queueable interface with an execute(QueueableContext ctx) method; add implements Database.AllowsCallouts if the job makes HTTP callouts
2. Pass required state (record IDs, configuration values) via constructor parameters stored as instance variables so the job has its context when execute() is called by the platform
3. Inside execute(), perform the primary work (SOQL, DML, callouts), then conditionally enqueue the next job in the chain using System.enqueueJob(new NextQueueable(results))
4. Gate chaining on a condition (e.g., there are more records to process) to avoid infinite job chains; include a depth counter as a constructor parameter if needed
5. Use Database.getAsyncApexJobId(ctx.getJobId()) if you need to store or return the job ID for monitoring via AsyncApexJob SOQL queries
6. Test Queueable jobs by calling System.enqueueJob() inside Test.startTest() / Test.stopTest() to force synchronous execution of the async job within the test context