Not sure if this applies to their use case since they mention FIFO in the context of it being a simple eviction policy, but if you _require_ FIFO semantics then

Not sure if this applies to their use case since they mention FIFO in the context of it being a simple eviction policy, but if you _require_ FIFO semantics then both Redis and memcached are out of the question since they use nondeterministic LRU policies (memcached's LRU is particularly egregious in its nondeterminism due to the way slab allocation works).