ElastiCache | Notion

Amazon ElastiCache Overview

Amazon ElastiCache is a managed service that simplifies the deployment and scaling of in-memory cache environments. It supports two popular caching engines: Redis and Memcached. These caches serve as in-memory databases, offering high performance and low latency to enhance application responsiveness, particularly for read-heavy workloads. By caching frequent queries, ElastiCache reduces the demand on databases, which can improve application performance and scalability.

Key Aspects of Amazon ElastiCache

Purpose: Helps in reducing database load by caching common queries, leading to faster data retrieval and improved application performance.
Statelessness: Facilitates application statelessness by storing session state in the cache, enabling seamless user experiences across different application instances.
Management and Maintenance: AWS handles operating system maintenance, patching, configuration, monitoring, failure recovery, and backups for ElastiCache, similar to RDS.

Application Code Changes

Integrating ElastiCache into an application requires significant code modifications. Applications must be adapted to query the cache before hitting the database, involving strategic changes in data fetching and cache invalidation processes.

ElastiCache Architecture Examples

Cache Usage for Database Queries:
- Application checks ElastiCache for data before querying the database.
- A "cache hit" avoids database queries, fetching data directly from ElastiCache.
- In case of a "cache miss," data is fetched from the database and then cached for future queries.
Session Data Caching for Stateless Applications:
- Session data from user logins is stored in ElastiCache.
- Allows other instances of the application to retrieve session data from the cache, maintaining user sessions across application instances.

Redis vs. Memcached

Feature	Redis	Memcached
High Availability	Multi-AZ with Auto-Failover	Not available
Read Scalability	Supports Read Replicas	Sharding for data partitioning
Data Durability	AOF persistence for data durability	No data persistence
Backup and Restore	Supported	Not supported
Data Structures	Supports sets, sorted sets, etc.	Basic key-value store
Use Cases	High availability, data durability	Pure caching, where data loss is acceptable

Conclusion

Amazon ElastiCache provides a highly available, scalable, and managed in-memory data store or cache environment, significantly enhancing application performance and scalability. Choosing between Redis and Memcached depends on specific application needs such as data durability, backup requirements, and whether high availability is critical. Redis offers a feature-rich environment with data persistence, backup, and high availability options, making it suitable for more complex use cases. In contrast, Memcached provides a simpler, distributed caching solution ideal for scenarios where temporary data can be stored without the need for persistence or high availability.