The Streaming Nightmare
One night, millions of users logged in to stream the final episode of a popular show. But instead of smooth playback, they got buffering.
The reason? The servers couldn’t handle the load. Every request hit the database, causing delays.
The solution? Distributed caching. By caching content closer to users, responses became lightning-fast.
What is Distributed Caching?
Distributed caching spreads cached data across multiple servers to handle high traffic and prevent bottlenecks.
It ensures:
Scalability – Supports millions of users.
High Availability – Prevents single points of failure.
Faster Access – Delivers content with minimal delay.
How Distributed Caching Works
A user requests data.
The system first checks the cache.
If data is found (cache hit), it is returned instantly.
If not found (cache miss), data is fetched from the database and stored in the cache for future use.
This reduces database load and speeds up responses.
You may refer to above diagram for this.
Distributed Caching Technologies
1. Redis – High-Speed In-Memory Store
Redis is an open-source, in-memory key-value store that supports advanced caching features.
Key Features:Data Persistence – Optionally saves data to disk.
Supports Expiration – Data can be auto-removed.
Pub/Sub Messaging – Enables real-time event handling.
✔ Caching database queries. ✔ Session storage for web apps. ✔ Leaderboards and real-time analytics.
{
"user123": "Ankit"
}2. Memcached – Lightweight and Fast
Memcached is another high-performance, in-memory caching system but is simpler than Redis.
Key Features:Super-fast, minimal overhead.
Multi-threaded for handling large traffic.
Best for simple key-value caching.
✔ Speeding up API responses. ✔ Caching user sessions. ✔ Reducing database load.
3. CDN-Based Caching – Global Scalability
Content Delivery Networks (CDNs) cache static and dynamic content on geographically distributed servers.
Key Features:Edge Caching – Stores content closer to users.
Reduces Latency – Faster access for global audiences.
Protects Origin Servers – Handles massive traffic loads.
✔ Streaming platforms like Netflix. ✔ E-commerce websites (Amazon, Shopify). ✔ News and media sites serving global audiences.
Comparison: Redis vs. Memcached vs. CDNs
Feature
Redis
Memcached
CDNs
Data Persistence
✔
✖
✖
Supports Expiry
✔
✔
✔
Distributed Scaling
✔
✔
✔✔✔
Best For
Data caching, real-time apps
Simple key-value caching
Large-scale content delivery
Real-World Use Cases
1. Social Media Platforms
Redis caches user profiles and notifications.
Memcached speeds up post-fetching.
CDNs serve images and videos worldwide.
2. E-Commerce Websites
Redis caches product details for instant access.
CDNs cache images, stylesheets, and JavaScript files.
3. Online Streaming Services
Redis stores session data for personalized recommendations.
CDNs deliver video streams with minimal lag.
Conclusion
Distributed caching ensures high performance, scalability, and resilience.
Redis is best for persistent and complex caching.
Memcached is lightweight and ideal for simple caching.
CDNs scale content delivery globally.
Next, we’ll explore Database Design & Optimizations – Indexing (B-Trees, Hash), Normalization vs. Denormalization.
