System Design - Scalability: Caching 1

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Questions and Answers

What is the primary goal of caching?

To reduce latency and improve response times, decrease the load on the primary data source, and improve overall performance and scalability of applications.

What type of caching is typically used to store frequently accessed database query results?

Database caching

What is the main difference between client-side caching and server-side caching?

Client-side caching is stored on the client (e.g., web browser), while server-side caching is stored on the server.

What is the purpose of a Content Delivery Network (CDN) cache?

To distribute copies of static content to edge servers around the world, reducing latency by serving content from the nearest edge server to the user. Signup and view all the answers

What is an example of a caching strategy that loads data into the cache only when requested by the application?

Cache-aside (lazy loading) caching Signup and view all the answers

What is the purpose of write-through caching?

To ensure data consistency between the cache and the primary data source by writing to both simultaneously. Signup and view all the answers

What is the main advantage of using a write-back cache?

It reduces the latency of write operations by acknowledging the write as soon as the data is written to the cache. Signup and view all the answers

What is an example of server-side caching?

Redis or Memcached Signup and view all the answers

What is the primary benefit of caching in terms of application performance?

Reduced latency and improved response times Signup and view all the answers

What is an example of client-side caching?

Browser cache or mobile app cache Signup and view all the answers

What is the main benefit of using a write-back cache?

Improves write performance Signup and view all the answers

What is the primary advantage of a read-through cache?

Simplifies application logic Signup and view all the answers

What is the purpose of a cache eviction policy?

Determines how data is removed from the cache when it reaches its capacity Signup and view all the answers

What is the first step in implementing effective caching?

Determine what to cache Signup and view all the answers

Why is it essential to implement cache invalidation strategies?

To ensure data freshness and accuracy Signup and view all the answers

What is the primary advantage of distributed caching?

Horizontal scalability and high availability Signup and view all the answers

How can database indexing optimize caching?

By speeding up query processing and reducing the need for caching Signup and view all the answers

What is the purpose of hybrid caching architectures?

To combine multiple caching strategies for optimized performance Signup and view all the answers

How do e-commerce websites typically use caching?

To cache product details, user sessions, and shopping carts Signup and view all the answers

What is the ultimate goal of implementing caching in system design?

To enhance performance, reduce latency, and improve scalability Signup and view all the answers

Study Notes

Caching Definition and Purpose

Caching is the process of storing copies of data in a temporary storage location to reduce the time it takes to access this data.
The primary goals of caching are to:
- Reduce latency and improve response times.
- Decrease the load on the primary data source.
- Improve the overall performance and scalability of applications.

Types of Caching

Client-Side Caching:
- Stored on the client, such as in a web browser’s cache.
- Reduces the need to fetch resources from the server repeatedly.
- Examples: browser cache, mobile app cache.
Server-Side Caching:
- Stored on the server to speed up data retrieval for client requests.
- Reduces database load and accelerates dynamic content delivery.
- Examples: Redis, Memcached.
Database Caching:
- Stores frequently accessed database query results.
- Improves database read performance and reduces query processing time.
- Examples: database query cache, in-memory database.
Content Delivery Network (CDN) Caching:
- Distributes copies of static content to edge servers around the world.
- Reduces latency by serving content from the nearest edge server to the user.
- Examples: Cloudflare, Akamai.

Caching Strategies

Cache-Aside (Lazy Loading):
- Data is loaded into the cache only when requested by the application.
- If the data is not in the cache (cache miss), it is fetched from the data source and then stored in the cache for future use.
- Example: A web application querying a database only when a cache miss occurs.
Write-Through Cache:
- Data is written to both the cache and the primary data source simultaneously.
- Ensures data consistency between the cache and the data source.
- Example: Updating a product inventory count in both the cache and the database at the same time.
Write-Back (Write-Behind) Cache:
- Data is written to the cache initially, with changes propagated to the data source asynchronously.
- Improves write performance but risks data loss if the cache fails before the write is propagated.
- Example: Logging user actions to a cache, with periodic updates to the database.
Read-Through Cache:
- The application interacts only with the cache, which retrieves data from the data source if it is not present in the cache.
- Simplifies application logic by centralizing data access through the cache.
- Example: A caching layer intercepting all read requests and fetching from the database on cache misses.
Cache Eviction Policies:
- Determine how data is removed from the cache when it reaches its capacity.
- Common policies include:
  - Least Recently Used (LRU): Removes the least recently accessed items first.
  - First In, First Out (FIFO): Removes the oldest items first.
  - Least Frequently Used (LFU): Removes the least frequently accessed items first.

Best Practices for Caching

Determine What to Cache:
- Identify frequently accessed data that is expensive to retrieve or compute.
- Examples: User session data, product details, query results.
Set Appropriate TTL (Time-To-Live):
- Define expiration times for cached data to ensure it stays fresh.
- Avoids serving stale data and balances cache performance with data accuracy.
Cache Invalidation:
- Implement strategies to invalidate or update cached data when the underlying data changes.
- Examples: Cache invalidation on data update events, scheduled cache refreshes.
Monitor Cache Performance:
- Track cache hit rates, miss rates, and latency to evaluate caching effectiveness.
- Adjust cache configurations and strategies based on monitoring data.
Handle Cache Failures Gracefully:
- Ensure the application can continue functioning correctly if the cache is unavailable.
- Implement fallback mechanisms to fetch data directly from the primary data source.

Advanced Caching Techniques

Distributed Caching:
- Use a distributed cache to store data across multiple nodes for horizontal scalability.
- Ensures high availability and fault tolerance by replicating data.
- Examples: Redis Cluster, Amazon ElastiCache.
Application-Level Caching:
- Implement caching within the application logic to store computational results or frequently used data structures.
- Examples: Local in-memory caches, application-specific caching frameworks.
Database Indexing:
- Use database indexes to speed up query processing and reduce the need for caching.
- Balances the benefits of caching with optimized data retrieval techniques.
Hybrid Caching Architectures:
- Combine multiple caching strategies to optimize performance.
- Examples: Using both CDN caching for static content and server-side caching for dynamic content.

Real-World Examples

E-commerce Websites:
- Cache product details, user sessions, and shopping carts to improve page load times and handle high traffic during sales events.
- Use CDNs to serve static content like images and scripts.
Social Media Platforms:
- Cache user profiles, feeds, and media content to enhance user experience and reduce backend load.
- Implement distributed caching to manage large volumes of data and traffic.
News Websites:
- Cache frequently accessed articles, headlines, and metadata to ensure fast content delivery.
- Use write-through caching for real-time updates and consistency.

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