Choosing an outbound callout mechanism
How to pick the way Salesforce calls out: named credential endpoints and the callout: scheme, synchronous versus Queueable, future and platform event subscribers, callouts after uncommitted DML, async request plus callback for long jobs, outbound message versus platform event delivery, Event Relay to Amazon EventBridge, Flow HTTP Callout limits and Named Principal versus Per User identity.
Given a use case, identify the considerations when choosing the right option in making an outbound call to an external system.
~8 min read · 11 practice questions ·
What the exam expects
- Choose the outbound mechanism from the requirement: does a user wait for the answer, how long does the remote work take, and what does the target accept?
- Point callouts at named credentials, reuse one credential across resource paths, and pick Named Principal or Per User identity.
- Avoid callouts after uncommitted DML and in front of users when a partner throttles; pick Queueable, future or a platform event subscriber.
- Contrast outbound message and platform event delivery, and know when Event Relay or Flow HTTP Callout fits.
Key terms: named credential (endpoint URL plus a reference to an external credential holding authentication); callout: URL (the scheme Apex uses to reference a named credential); Named Principal / Per User (one shared identity versus each user's own credential); Event Relay (low-code stream of events to Amazon EventBridge); callback (the remote system calls Salesforce back when its work finishes).
Key facts
- Detail
- Remote Site Settings required unless the endpoint is a named credential
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callout:Name/path?query; path and query vary per request
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- One admin credential for all users
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- No callout after DML, async Apex, scheduled Apex or email in the same transaction
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- 120 seconds maximum
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- Primitives, arrays or collections of primitives only
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Database.AllowsCallouts; job ID fromSystem.enqueueJob
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- Salesforce retries until the endpoint acknowledges; 24-hour replay period
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- Published once, no Salesforce retry; replay within 72 hours
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- Amazon EventBridge only
Sources for this section (9)
- Invoking Callouts Using Apexdeveloper.salesforce.com (opens in a new tab)
- Named Credentials as Callout Endpointsdeveloper.salesforce.com (opens in a new tab)
- Authentication Protocolshelp.salesforce.com (opens in a new tab)
- Callout Limits and Limitationsdeveloper.salesforce.com (opens in a new tab)
- Asynchronous Callout Limitsdeveloper.salesforce.com (opens in a new tab)
- Future Methodsdeveloper.salesforce.com (opens in a new tab)
- Queueable Apexdeveloper.salesforce.com (opens in a new tab)
- Integration Patternsarchitect.salesforce.com (opens in a new tab)
- Event-Driven Architecture Decision Guidearchitect.salesforce.com (opens in a new tab)
- Why does a hard-coded endpoint fail with "Unauthorized endpoint" while a named credential works?
- When should an outbound integration use Event Relay?
- Why convert a future method to Queueable when the job must carry sObjects and be monitored?
- When does a remote job need a callback instead of a callout that waits?
The questions are free to read. Answers with their sources and self-grading are included with the pack.
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