trigger cloud function directly or put in pub sub queue to trigger

[decentgradient]

I want to trigger a cloud function after receiving payment to continue processing an order...
Is there any reason to place a message in a pub sub queue rather than triggering the function directly?

[Marramirez]

Hello @decentgradient,

Welcome to Google Cloud Community!

Take a look at the documentation: Pub/Sub triggers. When you specify a Pub/Sub trigger for a function, you also specify a Pub/Sub topic. Your function will be called whenever a message is published to the specified topic.

Additionally, you can take a look at Cloud Function and Pub/Sub to better understand their difference. 

You can also contact Google Cloud Support to further look into your query. Hope it helps, thanks!

[knet]

What are some reasons you're thinking of for using a queue?

Cloud Functions scale very well to even a large number of invocations at the same time. There's no need for a PubSub queue if the goal is to manage Cloud Functions capacity.

A reason to use a PubSub queue (or Cloud Tasks) could be if you have a downstream resource that the function calls, and that resource can't deal well with too many requests in parallel.

I think there might be other use cases around decoupling systems and having multiple subscribers to that queue.

But the simplest thing here is: don't use a queue; you can always add one later if you find a need for it.