Manual:$wgMainStash

Details
This setting controls the cache used by methods that store temporary values that need to be seen in all datacenters. This is not true of $wgMainCacheType, which should be a fast and local-only cache. Ideally, a better effort should be made to reduce evictions are data loss during power outages that main cache stores (e.g. redis with disk-persistence enabled and ). Nevertheless, the store does not need to be a robust ACID compliant database, it should merely be a fast, memory-based, store that replicates data to all sites. A modest amount of eviction or lost data (such as on fail-over) can be tolerated.