Question 1

What's the difference between Pub/Sub and a message queue?

Accepted Answer

A message queue usually has one consumer (or a competing group) that processes each message, which is great for work distribution. Pub/Sub is designed for fan-out: one publisher can send a message that multiple subscribers each receive and process independently. In practice, many platforms (including Google Cloud Pub/Sub) can support both patterns, but the key idea of pub/sub is decoupling and broadcasting events to multiple consumers.

Question 2

When should I use Pub/Sub?

Accepted Answer

Use Pub/Sub when you want services to communicate asynchronously, especially when you need to: (1) decouple producers and consumers so they can scale independently, (2) broadcast the same event to multiple systems (e.g., analytics, notifications, fulfillment), (3) buffer traffic spikes so backends don’t overload, or (4) build event-driven pipelines where new consumers can be added without changing the publisher.

Question 3

How much does Pub/Sub cost?

Accepted Answer

Cost is mainly based on usage: how much data you publish and deliver, how many operations you perform, and any additional features you enable (for example, message retention duration or cross-region/network egress). Pricing varies by cloud provider and region, so the practical approach is to estimate monthly message volume (messages per second and average size), number of subscribers (fan-out increases deliveries), and any data egress to other regions or the internet.

Pub/Sub

Definition

Real-World Example

Cloud Provider Equivalencies

See Pub/Sub in Action

Production Microservices on Kubernetes

Secure GCP VPC with HTTPS LB, App & AI Subnets

Private VPC Web App with GPU AI Processing on GCP

Sionic Demo Env 2 GCP Web App Architecture

Explore More Cloud Computing Terms