Incremental Static Regeneration (ISR) enables to statically generate Next.js application on a per-page basis, without the need to re-generate it entirely from scratch. In other words, with ISR the content of a page in Next.js can be generated on-demand at the application runtime, instead of generating it when the application is being statically built.
This Next.js feature is an excellent fit for e-commerce. Let's imagine that our storefront must show thousands of products. If we assume that 50ms is needed to statically generate a product page, with a store showcasing 100,000 products, it will take almost 2 hours to build the entire storefront. ISR provides us with flexibility regarding the build time of our storefront.
We can for decide generate a small amount of products ahead-of-time. For example, we may select a subset of 1,000 most popular products in our store. This will greatly reduce the time needed for the build. In this particular case from almost 2 hours to just 1 minute. And the products that are not included in that list will be generated on-demand and then cached.