How would you implement caching in a distributed backend system to improve performance? Discuss different caching strategies, where to apply them, and their potential drawbacks.

``` Incorporate a layered caching strategy using in-memory caching (like Redis) for frequently accessed data and CDN for static assets; both can reduce database load and improve access speed. Scenario Pressure: What would you do if cache invalidation becomes a concern? Depth Trigger: Explain the concept of cache stampede and how you would mitigate it. ```