Garnet is Microsoft Research's cache-store built on .NET that speaks the Redis RESP wire protocol while delivering up to 10x higher throughput and 4x lower tail latency than comparable alternatives on identical hardware. The Tsavorite storage engine provides a cache-friendly, shared-memory architecture scaling linearly across CPU cores, supporting both in-memory operation and tiered storage across local SSDs and Azure Storage for datasets exceeding available RAM. Cluster mode enables sharded deployments with replication, dynamic key migration for live rebalancing, non-blocking checkpointing, and automatic failover using standard Redis cluster commands. The RESP implementation covers raw strings, sorted sets, lists, hashes, sets, bitmaps, HyperLogLog, streams, pub/sub, Lua scripting, and client-side transactions, allowing StackExchange.Redis, Jedis, redis-py, and other Redis clients to connect without modification. C#-based extensibility lets developers define custom commands and new data types as server-side stored procedures, compiled and loaded at runtime without restarting the server. TLS encryption, ACL-based access control, and operation logging complete the production feature set. Deployed across Microsoft services including Windows & Web Experiences, Azure Resource Manager, and Azure Resource Graph. Nearly 12,000 GitHub stars. MIT licensed.