Opensolr does not bill by the number of requests. It bills the bytes your index sends back. A tight query and a sloppy one cost the same to make, but not the same to answer.
One gigabyte of bandwidth is a million lean responses, or one heavy one. What you ask for decides which.
On a pre-paid plan you are billed for the outgoing bytes sent from your Opensolr index to your site or app. Nothing else. Not the number of queries, not the size of your index, not the traffic your own site receives.
Whoever reaches your search page, human or bot, triggers a query. The response coming back from the index is the part that counts.
- Bots and crawlers visit search pages far more than people do, and each visit becomes a query against your index.
- Heavy responses multiply that. A search page that returns full documents with every field makes every bot visit expensive.
- A sudden overnight spike is almost always a crawler loop or a scripted attack on the search page, not real visitors.
- Read the bandwidth saving tips: field lists, paging, filters and caching, in the order they usually pay off.
- Follow the best practices guide when you build the queries in the first place.
- Find the source in your logs before you tune anything. Opensolr logs every request to your index, and you can see all of it in three places below.
Query, facet and analyze your request log by any field. Facet by IP and path and you can see exactly who is eating the bandwidth. API documentation

The request log faceted by IP address and request path.
Traffic over time, spikes, popular queries and the pages behind them, per index, inside your control panel. Real time monitoring and analytics

Traffic and query analytics for one index.

Popular queries and where the traffic comes from.
The last 1,000 lines of the live request log, straight from the control panel. Watch traffic as it happens and spot a loop or an attack the moment it starts.

The live request log, as it comes in.

The same log, filtered down to one source.
If the numbers still do not add up, contact us with the index name and we will look at the log with you.