In serverless platforms, billing is usually based on a pay-as-you-go model. This means you are charged for the actual resources and computing power you use, rather than paying for fixed server instances. Here's how it typically works:

Compute Time: You're billed based on the amount of time your serverless functions or applications run. This is often measured in milliseconds, so you pay for the exact execution time of your code.

Memory Usage: The amount of memory your functions use also affects the cost. The more memory you allocate to a function, the higher the price.

Number of Invocations: Each time your function is triggered, you incur a cost. The more your functions are called, the more you pay.

Network Usage: Data transfer in and out of your serverless functions can also contribute to the cost.

Additional Services: If you use additional services within the serverless platform, like databases or storage, you'll be charged separately for those services.

Free Tier: Many serverless platforms offer a free tier with specific limits. If you stay within these limits, you won't incur any charges.

Billing can vary from one serverless provider to another, so it's essential to check the specific pricing details for the platform you're using. It's also a good practice to monitor your usage and set up alerts to avoid unexpected costs.