Choose Cloud Tasks or Pub/Sub

Both Cloud Tasks and Pub/Sub may be used to implement message passing and asynchronous integration, but while they function in similar ways, they are not identical. This page helps you choose the right product for your use case.

Key Differences

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

Pub/Sub aims to decouple publishers of events and subscribers to those events. Publishers do not need to know anything about their subscribers. As a result, Pub/Sub gives publishers no control over the delivery of the messages save for the guarantee of delivery. In this way, 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.

In addition, Cloud Tasks provides tools for queue and task management unavailable to Pub/Sub publishers, including:

  • Scheduling specific delivery times
  • Delivery rate controls
  • Configurable retries
  • Access and management of individual tasks in a queue
  • Task/message creation deduplication

Detailed feature comparison

Feature Cloud Tasks Cloud Pub/Sub
Push via webhooks Yes Yes
At least once delivery guarantee Yes Yes
Configurable retries Yes Yes
Task creation deduplication Yes No
Scheduled delivery Yes No
Ordered delivery No. Enqueued task order is preserved on best-effort basis. Yes with ordering keys
Explicit rate controls Yes Pull 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 31 days
Max size of task/message 1MB 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 1,000/project, more available via quota increase request 10,000/project