Choosing between Cloud Tasks and Cloud Pub/Sub

Both Cloud Tasks and Cloud Pub/Sub can be used to implement message passing and asynchronous integration. Although they are conceptually similar, each is designed for different set of use cases. This page helps you choose the right product for your use case.

Key Differences

The core difference between Cloud Pub/Sub and Cloud Tasks is in the notion of implicit vs. explicit invocation.

Cloud Pub/Sub aims to decouple publishers of events and subscribers to those events. Publishers do not need to know anything about their subscribers. Therefore, Cloud Pub/Sub gives publishers no control over the delivery of the messages save for the guarantee of delivery. In this way, Cloud Pub/Sub supports implicit invocation: a publisher implicitly causes the subscribers to execute by publishing an event.

By contrast, Cloud Tasks is aimed at explicit invocation where the publisher retains full control of execution. In particular, a publisher specifies an endpoint where each message is to be delivered.

Overall Cloud Tasks are appropriate for use cases where a task producer needs to defer or control the execution timing of a specific webhook or remote procedure call. Cloud Pub/Sub is optimal for more general event data ingestion and distribution patterns where some degree of control over execution can be sacrificed.

Detailed feature comparison

Feature Cloud Tasks Cloud Pub/Sub
Push via webhooks Yes Yes
At least once delivery guarantee Yes Yes
Task creation deduplication Yes No
Configurable retries Yes No
Scheduled delivery Yes No
Explicit rate controls Yes No (Subscriber clients can implement flow control)
Pull via API No Yes
Batch insert No Yes
Multiple handlers/subscribers per message No Yes
Task/message retention 30 days Up to 7 days
Max size of task/message 100KB 10MB
Max delivery rate 500 qps/queue No upper limit
Geographic availability Regional Global
Maximum push handler/subscriber processing duration 30 minutes (HTTP)
10 minutes (App Engine Standard automatic scaling)
24 hours (App Engine Standard manual or basic scaling)
60 minutes (App Engine Flexible)
10 minutes for push operations
Number of queues/subscriptions per project 100/project, more available via quota increase request 10,000/project
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Cloud Pub/Sub Documentation