Both Cloud Tasks and 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 Pub/Sub and Cloud Tasks is in 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. Therefore, Pub/Sub gives publishers no control over the delivery of the messages save for the guarantee of delivery. In this way, Pub/Sub supports implicitinvocation: a publisher implicitly causes the subscribers to execute by publishing an event.
By contrast, Cloud Tasks is aimed at explicitinvocation 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. 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 | Pub/Sub |
|---|---|---|
|
Push using webhooks
|
Yes | Yes |
|
At-least-once delivery guarantee
|
Yes | Yes |
|
Configurable retries
|
Yes | Yes |
|
Task/message creation deduplication
|
Yes | No |
|
Scheduled delivery
|
Yes | No |
|
Ordered delivery
|
No, enqueued task order is preserved on a best‑effort basis | Yes, with ordering keys |
|
Explicit rate controls
|
Yes | Pull subscriber clients can implement flow control |
|
Pull using API
|
No | Yes |
|
Batch insert
|
Yes | Yes |
|
Multiple handlers/subscribers per message
|
No | Yes |
|
Task/message retention
|
31 days | Up to 31 days |
|
Maximum size of task/message
|
1MB | 10MB |
|
Maximum delivery rate
|
500 QPS/queue | No upper limit, subject to regional throughput quotas |
|
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
|
1,000 per project per region, more available through quota increase request | 10,000 per project |
