My main use case for Redis is caching frequently accessed data to improve performance and reduce database load. For example, I cache API responses and user-related data so that repeated requests can be served quickly without hitting the database every time. I use TTL to automatically expire stale data and ensure caching freshness. In some cases, I also use Redis for session management and handling short-lived data efficiently.
I have used Redis for session management in a back-end system, where the main idea was to store user session data in Redis instead of keeping it in memory on a single server, which helps me scale across multiple instances. When a user logs in, we generate a session ID or token and store session-related data like user ID and metadata in Redis, and this session is associated with a TTL. It automatically expires after a certain period of time or after a certain time of inactivity. On each request, the session ID is validated by fetching data from Redis, which is very fast due to its in-memory nature, ensuring low latency and allowing us to handle the highest traffic efficiently. This approach helps us achieve horizontal scalability and avoids issues concerning session stickiness. Additionally, we ensure security by expiring inactive sessions or occasionally refreshing TTL for active users.
Apart from caching and session management, I worked on interesting challenges using Redis, particularly around caching consistency and handling stale data. Initially, we faced issues where cached data would become outdated after database updates, and to solve this, we implemented a cache-aside strategy where we explicitly invalidated or updated the cache whenever the underlying data changed. Another scenario was handling cache misses during high traffic to avoid multiple requests hitting the database simultaneously, where we introduced techniques such as setting approaches, TTLs, and in some cases, using locking to ensure only one request rebuilds the cache. We also tuned invocation policies and memory usage to ensure Redis remains performant under load. These experiences helped me understand how to use Redis not just as a cache, but as a critical component in system performance and scalability. For maintaining the high traffic system, we also explored using Redis for rate limiting and short-lived counters, which further reduced our load on our core system.