Streaming API Developer Guide

Getting Started with Streaming API
Push Technology
Bayeux Protocol, CometD, and Long Polling
Streaming API Terms
How the Client Connects
Message Reliability
Message Durability
Streaming Event Features
Streaming API vs. Pub/Sub API
Differences Between Change Events Received with Streaming API vs. Pub/Sub API
API End-of-Life Policy
Code Examples
Client Connection Considerations
PushTopic Events (Legacy)
Generic Events (Legacy)
Monitoring Event Usage
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Streaming API vs. Pub/Sub API

Pub/Sub API is a newer API that you can use to publish and subscribe to platform events and change data capture events. Based on gRPC API and HTTP/2, Pub/Sub API efficiently publishes and delivers binary event messages, and supports multiple programming languages. Before Pub/Sub API was introduced, the only way to subscribe to events in an external client was with Streaming API. This table compares some features of the two subscription APIs.
Streaming API Pub/Sub API
Event encoding JSON Binary (Apache Avro)
Protocol CometD, an implementation of the Bayeux protocol. gRPC and protocol buffers
Subscription model Push-based—The server delivers events as they become available in the event bus. Pull-based—The client requests the number of events to receive as they become available in the event bus.
Subscription flow control The client doesn’t control the number of events delivered from the server. The client specifies how many events to receive for a Subscribe call based on event processing speed.
Publish status Not supported with Streaming API. When using data APIs to publish events, the event queueing result is returned. When system resources are available, queued events are published. The final result isn’t returned to the client. The final publishing result returned indicates that the event was successfully published or that the publish failed.