Practical guide
Estimate Pub/Sub cost from message throughput
Forecast Pub/Sub publishing, delivery, retention, subscriptions, and cross-region transfer with message-size assumptions.
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Throughput is publish plus delivery
Google prices Pub/Sub service throughput from published, delivered, and stored bytes, with data transfer and retention as additional considerations. The first 10 GiB of Message Delivery Basic throughput per billing account is free; use the current official rate after that.
For 2 TiB published to a topic with two subscribers, begin with publish quantity plus two delivery quantities, then account for subscription type, retention, and region crossings. Tiny messages have a documented minimum request size, so batching can alter billed throughput.
Use the Pub/Sub Cost Calculator with observed bytes and subscriber count. Check export subscriptions and storage separately.
FAQ
Does each subscriber add delivery?
Yes, delivery is a throughput component; calculate each applicable subscription path.