Amazon ElastiCache for Redis is a great choice for implementing a highly available in-memory cache to decrease access latency, increase throughput, and ease the load off your relational or NoSQL database. Amazon ElastiCache can serve frequently requested items at sub-millisecond response times, and enables you to easily scale for higher loads without growing the costlier backend database layer. Database query results caching, persistent session caching and full-page caching are all popular examples of caching with ElastiCache for Redis.

Real-time leaderboards are easy to create with Amazon ElastiCache for Redis. Simply use the Redis Sorted Set data structure, which provides uniqueness of elements while maintaining the list sorted by their scores. Creating a real-time ranked list is as easy as updating a user's score each time it changes. You can also use Sorted Sets to handle time series data by using timestamps as the score.

You can use Amazon ElastiCache for Redis to implement a rate limiter when building your own API or consuming a third-party API offering. By using a Redis counter associated with a client's API key, you can count the number of access requests within a certain time period and take action if a limit is exceeded. Rate limiters are commonly used for limiting the number of posts on a forum, limiting resource utilization and containing the impact of spammers.

ElastiCache for Redis makes it easy to implement a lightweight, persistent queue using the Redis List data structure. Lists offer atomic operations as well as blocking capabilities, making them suitable for a variety of applications that require a reliable message broker or a circular list.

Redis supports the PUB/SUB standard along with pattern matching. This allows you to use ElastiCache for Redis for designing high performance chat rooms, real-time comment streams, server intercommunication and more. You can also use PUB/SUB to trigger actions based on published events.