Platform Cache Internals

Local Cache

Platform Cache uses local cache to improve performance, ensure efficient use of the network, and support atomic transactions. Local cache is the application server’s in-memory container that the client interacts with during a request. Cache operations don’t interact with the caching layer directly, but instead interact with local cache.

For session cache, all cached items are loaded into local cache upon first request. All subsequent interactions use the local cache. Similarly, an org cache get operation retrieves a value from the caching layer and stores it in the local cache. Subsequent requests for this value are retrieved from the local cache. All mutable operations, such as put and remove, are also performed against the local cache. Upon successful completion of the request, mutable operations are committed.

Atomic Transactions

Each cache operation depends on the Apex request that it runs in. If the entire request fails, all cache operations in that request are rolled back. Behind the scenes, the use of local cache supports these atomic transactions.

Eviction Algorithm

When possible, Platform Cache uses an LRU algorithm to evict keys from the cache. When cache limits are reached, keys are evicted until the cache is reduced to 100-percent capacity. If session cache is used, the system removes cache evenly from all existing session cache instances. Local cache also uses an LRU algorithm. When the maximum local cache size for a partition is reached, the least recently used items are evicted from the local cache.