How does ElastiCache aim to relieve backend databases?

ElastiCache is designed to enhance application performance by caching frequently accessed data in memory, which significantly reduces the load on backend databases. When frequently queried data is stored in-memory, applications can retrieve this data much faster compared to accessing it from a disk-based database. This leads to lower latency and improves response times for users, enabling the backend database to handle more transactions and operate efficiently without becoming a bottleneck.

Caching reduces the number of read operations made to the database, which can alleviate performance constraints, especially during peak usage times. By serving requests for common data directly from the cache, ElastiCache minimizes the number of queries sent to the backend database, which ultimately boosts scalability and performance.

Other options like encrypting data at rest, decreasing the number of data sources, or hosting static content do not directly contribute to relieving the backend database. While encryption is crucial for security, it doesn't address performance; decreasing data sources might complicate the system architecture rather than improve it; and hosting static content relates more to content delivery rather than database management. Therefore, caching frequently accessed data in-memory is the ideal approach that ElastiCache employs to relieve backend databases.