Context

When using websocket connections with subscription methods like eth_subscribe, you may notice higher than expected API credit usage for that method, particularly when subscribing to events like newHeads and on fast blockchains.

Answer

Subscription methods through websockets are billed differently than regular API calls. While you only send one eth_subscribe request to initiate the subscription, you are charged for each response received through that subscription.

For example:

• When you subscribe to newHeads, you'll be charged for each new block header received, this response will appear in your dashboard metrics as eth_subscribe

• For pending transactions subscriptions, you'll be charged for each transaction notification delivered via the websocket connection.

If you're seeing unexpectedly high usage, consider:

• Using polling instead of subscriptions for less frequent updates

• Implementing filters to receive only specific events you need

• Being mindful of subscription types on high-throughput networks which generate many events

Check out these resources for more information:
How to Filter Mempool Transactions on Ethereum

WebSocket vs. QuickNode Streams