API-based integration and event-based integration are two core approaches in Salesforce, each suited to different scenarios.
API-Based Integration
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Model: Request–Response (synchronous)
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How it works: One system calls Salesforce (or vice versa) using APIs like REST, SOAP, or Bulk API, and waits for a reply.
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Example: An e-commerce app calling Salesforce REST API to create an Order.
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Best for: Real-time queries, direct updates, data synchronization, when you need immediate feedback.
Event-Based Integration
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Model: Publish–Subscribe (asynchronous)
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How it works: Salesforce publishes events (via Platform Events or CDC), and subscribers automatically react.
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Example: An update in an Opportunity publishes an event → a marketing app listens and sends a follow-up email.
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Best for: Real-time notifications, multi-system reactions, scalable and loosely coupled architectures.
Key Differences
| Aspect | API-Based Integration | Event-Based Integration |
|---|---|---|
| Model | Request–Response | Publish–Subscribe |
| Synchronicity | Typically synchronous | Asynchronous |
| Coupling | Tighter (direct system-to-system calls) | Loosely coupled (publisher doesn’t know subscribers) |
| Real-time | Immediate but requires explicit call | Real-time push notifications |
| Error Handling | Immediate feedback | Requires monitoring/retry mechanisms |
Analogy
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API-based → Like calling a restaurant to ask “Is my order ready?” (direct, immediate).
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Event-based → Like the restaurant texting you automatically when your order is ready (asynchronous, decoupled).
In practice: Most Salesforce integrations use a mix of both — APIs for direct data exchange and events for real-time triggers/notifications.
Interview Questions & Answers
1. What is the difference between API-based and event-based integration in Salesforce?
Answer:
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API-based integration uses a request–response model where one system makes an API call (REST, SOAP, Bulk) to interact with Salesforce synchronously.
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Event-based integration uses a publish–subscribe model where Salesforce publishes events (via Platform Events or Change Data Capture) and subscribers react asynchronously.
2. When would you prefer API-based integration over event-based integration?
Answer:
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Use API-based when you need immediate feedback, synchronous transactions, or direct CRUD operations (e.g., inserting records, querying data).
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Example: Payment processing, where you need to know instantly if the payment succeeded.
3. When would you prefer event-based integration over API-based integration?
Answer:
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Use event-based when you need real-time notifications, decoupled systems, or multiple subscribers reacting to the same change.
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Example: A new Opportunity created in Salesforce automatically triggers downstream marketing and billing systems.
4. What are the advantages and disadvantages of API-based integration?
Answer:
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✅ Advantages: Real-time data, simple to implement, immediate error feedback.
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❌ Disadvantages: Tight coupling, dependency on system availability, scalability issues if many calls are made.
5. What are the advantages and disadvantages of event-based integration?
Answer:
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✅ Advantages: Loose coupling, scalable, multiple subscribers can react to the same event, real-time push notifications.
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❌ Disadvantages: Asynchronous (no immediate response), requires event monitoring/retry mechanisms, slightly more complex setup.
6. Can API-based and event-based integrations be used together?
Answer:
Yes. In most real-world Salesforce implementations, a hybrid approach is used.
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Example: Use event-based (CDC) to notify systems about data changes. Then those systems use API-based calls if they need additional details or to perform follow-up actions.
7. Which Salesforce features support event-based integration?
Answer:
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Platform Events (custom event definitions for business processes).
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Change Data Capture (CDC) (publishes record changes automatically).
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Streaming API (push topics based on SOQL).
8. How does error handling differ between API-based and event-based integrations?
Answer:
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API-based: Errors are returned immediately in the response (e.g., 400, 401, 500).
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Event-based: Errors must be handled via subscriber retry logic, dead-letter queues, or event replay (since the publisher doesn’t know the subscriber failed).
9. Which integration is better for scalability?
Answer:
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Event-based → better for scaling across multiple subscribers and decoupled systems.
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API-based can scale, but may hit API limits or require orchestration.
10. Quick Analogy Question (common in interviews)
Q: “How would you explain API-based vs Event-based integration to a non-technical stakeholder?”
Answer:
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API-based is like calling a restaurant to ask if your food is ready (direct, immediate response).
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Event-based is like the restaurant texting you when your food is ready (automatic, asynchronous).
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