What it is. Data moving from your origin or serverless function into Vercel's edge network, billed separately from the bandwidth that then goes out to the visitor.
Why it surprises people. It bills the internal leg of the journey. An uncached response that pulls a large payload from a database on every request bills twice over: once as Fast Origin Transfer coming from your function, once as bandwidth going out to the user.
Most people never look at this line until it is large.
What makes it go up.
- Cache misses. Overwhelmingly the main cause.
- Large API responses generated per request.
- Server-rendered pages that could have been static or cached.
- Fetching more data than you render.
How to reduce it.
- Cache. This line item is close to a direct readout of your cache miss rate.
- Return less. Select the fields you need rather than whole records.
- Static-render anything that does not genuinely need to be per-request.
- Compress large API responses.
A near-zero Fast Origin Transfer figure means your caching is working. A large one is a diagnosis, not just a charge.
Watch it before it bites
MONII tracks Vercel and Netlify usage and alerts at a threshold you choose, with a kill switch to pause a runaway project.
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