Speeding Up Systems With Smart Storage
Caching involves storing frequently accessed data in a fast cache to reduce access latency. Improves system performance by minimizing data retrieval time. Reduces redundancy in data access.
Key Terms
1. Cache Miss
What It Is: Occurs when requested data isn’t found in the cache.
Impact: Requires fetching data from slower main memory, increasing latency.
2. Cache Hit
What It Is: Happens when requested data is found in the cache.
Impact: Allows quick retrieval, reducing access time.
3. Cache Invalidation
Definition: Marking cached data as invalid or outdated.
Purpose: Ensures that stale data isn’t used.
Cache Eviction Policy
Purpose: Decides which items to remove from the cache when full.
- LRU (Least Recently Used): Evicts least recently accessed item.
- LFU (Least Frequently Used): Evicts least frequently accessed item.
- FIFO (First-In-First-Out): Evicts the oldest item.
- Random Replacement: Evicts a random item.
- MRU (Most Recently Used): Evicts most recently accessed item.
Cache Write Strategy
- Write Through: Writes to both cache and main memory (ensures consistency, higher latency).
- Write Back: Writes to cache first, updates main memory later (fast but risk of inconsistency).
- Write Around: Writes directly to main memory, bypassing cache (avoids unnecessary caching).
Differences Between Cache and Databases
| Feature | Cache | Database |
|---|---|---|
| Purpose | Performance enhancement | Structured data storage |
| Data Durability | Sacrifices persistence | Prioritizes durability |
| Latency | Low | Higher |
| Data Management | Lightweight structures | Complex management |
| Lifespan | Short-term | Long-term |
Distributed Cache
Definition: A caching system across multiple nodes.
Benefits: Improves scalability, availability, and performance.
Caching Tools
- Redis: In-memory store, supports data structures, persistence, distributed caching.
- Memcached: Optimized for quick lookups, distributed, no persistence.
Content Delivery Network (CDN)
Definition: Distributed servers for efficient content delivery.
Why CDNs Are Needed
- Reduces latency
- Global reach
- Scalability
- Load balancing
- Content caching
- Dynamic content acceleration
- Security & reliability
- Improved user experience
- Bandwidth savings
Examples of CDNs
Akamai, Cloudflare, Amazon CloudFront, Microsoft Azure CDN, KeyCDN, Cachefly.
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