Data pipelines sometimes get spikes in published traffic. The traffic spikes can overwhelm subscribers unless you're prepared for it. A simple solution to avoiding traffic spikes is to dynamically increase Pub/Sub subscriber resources to process more messages. However, this solution might drive up costs or not work instantaneously. For example, you might require many VMs.
Flow control on the subscriber side lets the subscriber regulate the rate at which messages are ingested. Flow control thus handles traffic spikes without driving up costs or until the subscriber is scaled up.
Flow control is an available feature in the Pub/Sub high-level client library. You can also implement your own flow control programming when you're using a