Dynamic updates to improve performance

Improving the performance of a web application that handles a large number of lessons with dynamic information can be challenging. Here are some strategies and refinements to the solutions you’ve proposed:

Initial Problem Analysis

• High Volume of Data: 200 lessons is manageable, but scaling to 1000 lessons could indeed strain the server and client-side performance.

• Data Immutability: Static lesson properties are rarely changed, whereas dynamic information like status and scores are updated frequently.

Proposed Solutions and Enhancements

1. Caching Strategy Enhancement

   • Rails.cache: Continue caching static lesson properties.

   • Cache Invalidation: Use a more granular cache invalidation strategy. Instead of invalidating the entire cache on any change, invalidate only the specific lesson or related fragments.

2. Fragment Caching

   • Redis: Store lesson nodes in Redis for quick access.

   • Cache Keys: Use unique keys that include both student ID and lesson ID to ensure that updates to one student’s progress don’t affect others.

3. Front-End Optimization

   • Initial Load: Load static content first from the server cache.

   • Dynamic Update: Use AJAX to request only the dynamic changes, updating the DOM as needed.

4. Front-End Frameworks

   • React/Vue: For more complex applications, using a front-end framework can help manage state and updates more efficiently.

5. Incremental Loading

   • Pagination or Infinite Scroll: Instead of loading all lessons at once, implement pagination or infinite scrolling to load lessons in chunks as the user scrolls.

6. WebSockets for Real-Time Updates

   • If the application requires real-time updates, consider using WebSockets to push updates to the client whenever a lesson’s status changes.

7. Database Optimization

   • Indexes: Ensure that the database has appropriate indexes for quick lookup of lessons based on status or other frequently queried fields.

   • Read Replicas: Use read replicas to distribute the load of database reads.

8. Selective Rendering

   • Only re-render components or parts of the page that have actually changed, rather than refreshing the entire list.

9. Service Workers

   • Use service workers to cache data on the client side, allowing for offline access and reducing server load.

10. API Design

    • Design the API to allow for fetching only the necessary data, such as endpoints for fetching only lessons that have changed since the last check.

Implementation Considerations

• Testing: Ensure that any caching strategy is thoroughly tested to avoid serving stale data.

• Monitoring: Implement monitoring to understand the impact of caching and to identify any performance bottlenecks.

• Fallbacks: Have a fallback mechanism in case the cache fails or becomes stale.

Example Code Snippet for Cache Invalidation

Here’s a simple example of how you might handle cache invalidation in Rails:

# When a lesson is updated

def update_lesson(lesson, attributes)

  lesson.update!(attributes)

  expire_fragment(["lesson", lesson.id]) # Invalidate the specific lesson fragment cache

end

And for the front-end, you might have an AJAX call that looks something like this:

function fetchUpdatedLessons() {

  fetch('/api/lessons/updated')

    .then(response => response.json())

    .then(data => {

      data.forEach(lesson => {

        updateLessonDOM(lesson); // A function to update the lesson's DOM node

      });

    });

}

// Call this function periodically or on specific triggers

setInterval(fetchUpdatedLessons, 10000); // Every 10 seconds

By combining these strategies, you can create a more efficient system that scales better as the number of lessons increases.