I'm making a call to Amazon's paapi on a Nextjs site hosted on Vercel. Like most API's, Amazon limits the number of transactions per second and per day. I'm using the amazon-paapi React library inside of an API route at pages/api/amazon-product.js.

I'm using Cache-Control to achieve this:

export default async function handler(req, res) {
    const { productId } = req.body

    const {commonParameters, requestParameters} = getRequestParams(productId)

    amazonPaapi.GetItems(commonParameters, requestParameters)
    .then(response => {
        // Cache response to reduce API calls
        res.setHeader('Cache-Control', 's-maxage=86400')
        return res.status(201).json({ data: response.ItemsResult.Items[0] })
    })
    .catch(error => {
        return res.status(400).json({
            error: error
        })
    });
}

Since res.setHeader() is inside of the amazonPaapi.GetItems() method, I'm wondering if it wouldn't cache because that method will be called regardless of whether what it returns is cached?

It seems like we'd want to check whether max age has expired before we call the amazonPaapi.GetItems() method. Is this the case? If so, how can we do this?