Incremental Static Regeneration (ISR) In Next.Js

Create/serve pre-rendered pages on demand, balancing real-time updates and performance.
SSG: Generate all pages during the build process.
SSR: Generate each page on every request.
ISR: On each page, indicate how frequently the page should be regenerated in the background.

Benefits

Real-time update the stale pages in the background.
Personalised content - Generate personalised static pages based on the user-specific data.
SEO-friendly.
Developer experience.
Reduce cost for the build process.

Cache invalidation
If there are API calls, then the compatibility/synchronisation can be challenging.
Increased complexity.
Server load.

No problems on authenticated fetches because we have user already.
Problem is on non-authenticated fetches like:
- Bootstrap
- Terms and conditions
- Help center/static documents
Biggest change is moving the folder structure of the pages.
- Long-term this allows us to move to full-route caching the pages (we are caching responses already anyway).
Middleware only is to add locale if there is no locale specified, and use negotiator to figure out what locale to add.
When we have locale in the params (not query params), we can access that anywhere in the server, even without the user.