In case you didn't already know, Cloud Pub/Sub includes two different offerings, Pub/Sub and Pub/Sub Lite. In this section, I'm going to talk about the differences between the two. Now, both Pub/Sub and Pub/Sub Lite are message queueing solutions. But, as the name suggests, Pub/Sub Lite is the less powerful option. Its main advantage is that it is more affordable.

Now, for complete details, you should check out this URL. In general, the Pub/Sub service should be your default choice. It offers the highest reliability and a wider range of options. You get per-message parallelism, global routing, and automatic capacity scaling. Pub/Sub Lite offers lower availability and durability. In addition, it requires you to manually reserve and manage resource capacity. However, Pub/Sub Lite can be as much as an order of magnitude less expensive. Here's a table to help you quickly understand the differences between the two.

You can see that Pub/Sub will replicate messages across multiple zones. Pub/Sub Lite is limited to a single zone. With Pub/Sub, you have automatic capacity provisioning. Where with Pub/Sub Lite, you have to do things manually. Now, that means in terms of cost, Pub/Sub is "pay for what you use." But Pub/Sub Lite is "pay for what you provision." If you provision more capacity than you end up using, you're gonna be spending more than you need to.

Pub/Sub has an unlimited storage limit for messages. Pub/Sub Lite gives you a little bit more than 10 terabytes per topic. Now, in Pub/Sub, messages can only be retained for up to seven days. In Pub/Sub Lite, you can actually make that unlimited retention. However, when it comes to message routing, Pub/Sub can route messages anywhere around the globe, but Pub/Sub Lite can only route messages within a zone. You need to understand the differences, as well as your specific needs, before choosing one versus the other.