Transparent Caching Analysis
It involves the automatic storage of certain query results. When the same query is executed again, the DB can serve results from the cache, instead of performing re-query.
Benefit of Transparent Query Caching 🔍
- Speed: Frequently executed queries return results faster as they are fetched from the cache.
- Reduced Load: Reduces the workload on the DB engine.
Appropriate Use-cases 🎯
This caching mechanism shines in read-heavy applications where:
- The same queries are executed frequently.
- Data doesn’t change often, minimizing cache invalidations.
MySQL’s Historical Use of Transparent Query Caching ⚖️
MySQL employed a memory-based structure for caching. When a SELECT query was made, MySQL would first inspect this cache. If the result was present, it was returned immediately; if not, the query proceeded as usual and might subsequently be cached.
Deprecation of MySQL’s Query Cache and Reasons ❌
MySQL deprecated its query cache starting from version 8.0 due to:
- Contention Issues: A global mutex lock during cache access caused bottlenecks in high concurrency environments.
- Invalidation Overhead: Frequent data updates could lead to the cache being invalidated and repopulated regularly, negating its benefits.
Leveraging External Caches and Their Advantages 🔧
Since MySQL removed out of the box support to transparent caching. Devs can use tools like Redis and Memcached, they even overcome the MySQL’s pitfalls:
- Granularity: Devs have control over cache content and invalidation, rather than broad automatic invalidations.
- Optimized Locking Mechanisms: Designed with high-concurrency in mind, avoiding global mutex contention issues.
- Flexible Invalidation: Rely on strategies like Time-To-Live (TTL) or custom logic, providing better control over cache lifespan.