The document discusses Ristretto, a high performance concurrent cache for Go. It aims to have fast access times, high concurrency and resistance to contention, while bounding memory usage. It uses TinyLFU for admission control and sampled LFU for eviction. Stores are sharded across mutex-wrapped maps for concurrency. Hashing uses memhash for speed. Gets and Sets use lossy ring buffers and channels to balance performance and scalability across goroutines. Metrics avoid false sharing overhead. Usage involves creating a cache, setting and getting values, and deleting values.