New Caching System for the Nextjs
The Full Picture of Caching in Next.js
Before exploring the new caching system provided by Next.js, it’s worth understanding the limitations of the old one and why this improvement was necessary. Why did Next.js go through the effort of introducing a new caching system?
Caching is a critical component of any performant web application. An effective caching mechanism reduces resource usage, ensures static content is served quickly via a CDN, and boosts overall performance. High performance directly translates to better SEO rankings for important keywords, improves the user experience, and significantly reduces server resource costs, particularly in serverless environments. With reduced server load, you can serve the same content with less infrastructure, minimizing operational costs—a benefit crucial for modern applications.
Four Types of Caching in Next.js
Next.js offers four distinct types of caching, each serving a specific purpose. Let’s break them down:
1. Request Memory Cache
The Request Memory Cache ensures that any data fetched with the same cache key within the same component tree is reused. This avoids making redundant resource calls, such as querying a database or server API. If a function is called multiple times with the same parameters within a single request, it will always return the cached result.
This eliminates the need to pass fetched data down through props in a complex pattern, offering more flexibility in component design. Even if you fetch data in an RSC (React Server Component), the result will still be cached and available for the RCC (React Client Component) during the initial load.
Key benefits:
- Avoid duplicate requests: Reduces unnecessary calls to data sources.
- Enhanced flexibility: No need to pass props through deep component hierarchies.
- Unified caching for RSC and RCC.
2. Data Cache
The Data Cache extends caching across requests and even across deployments. When a user request hits the Data Cache, Next.js serves the cached result instead of fetching fresh data from the original data source. The cache key is automatically determined by the parameters you pass to the fetch function or the unstable_cache function (soon to be replaced by useCache).
Key Challenges:
Since the Data Cache persists across requests, stale data can be a problem. For instance, if a user updates or creates a post, the cache might still serve old data until revalidation occurs.
To address this, Next.js provides Time-based Revalidation and On-Demand Revalidation mechanisms.
Time-based Revalidation: Automatically invalidates the cache after a specified expiration period. However, the first user after the expiration still receives stale data.
On-Demand Revalidation: Explicitly triggers cache invalidation, ensuring no user ever sees stale data.
3. Full Route Cache
The Full Route Cache is responsible for caching the HTML and RSC payloads of static routes. When a user accesses the same route segment, Next.js serves the cached HTML and RSC payload to speed up the response.
- HTML Cache: Quickly displays the user interface to the browser.
- RSC Payload Cache: Used to reconcile with the RCC on the browser during hydration.
Limitations:
The Full Route Cache only works for statically rendered routes. Dynamic routes, rendered on request, are not cached. Here’s what the documentation says:
Whether a route is cached or not at build time depends on whether it's statically or dynamically rendered. Static routes are cached by default, whereas dynamic routes are rendered at request time and not cached.
4. Client Router Cache
Next.js maintains an in-memory client-side router cache to store RSC payloads for route segments. This cache is divided into:
- Layouts
- Loading states
- Pages
The Client Router Cache ensures efficient page transitions by reusing data from the memory cache instead of fetching it anew.
Why is Caching So Important?
The new caching mechanisms in Next.js offer substantial benefits:
- Improved performance: Caching reduces redundant requests and speeds up page rendering.
- Cost efficiency: Minimizes server resource usage, especially in serverless environments.
- SEO optimization: Faster websites rank higher on search engines.
- Simplified development: Flexible and automated caching strategies reduce developer effort.
By understanding and utilizing these caching mechanisms, developers can build highly performant, scalable applications with minimal operational complexity.
Use Cache
It is a new caching system, we will talk it later.