Suggest an editImprove this articleRefine the answer for “Why is Redis considered very fast?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)Redis is considered very fast because its whole architecture is built for minimal latency: data lives in RAM (nanosecond access instead of millisecond disk access), commands are processed single-threaded (no locks or data races), and its data structures and the RESP protocol are optimized for efficient O(1)/O(log n) operations. **Key point:** as a result, Redis can handle hundreds of thousands of operations per second with sub-millisecond latency.Shown above the full answer for quick recall.Answer (EN)ImageRedis is considered **very fast**, because its architecture and implementation are entirely built around **minimal latency** and **maximum performance**. Here are the key reasons: ### 1. All data lives in RAM The main difference between Redis and classic databases. - Accessing RAM takes **nanoseconds**, while accessing disk takes **milliseconds**. - That gives a speedup of **thousands of times** for reads and writes. *The takeaway:* Redis is in-memory, so it runs as fast as a cache. ### 2. A single-threaded architecture Redis processes commands **in a single thread**, which rules out locks and data races. - Every operation is **atomic**, with no waiting on others. - There's no overhead from synchronizing threads. *The takeaway:* minimal latency and predictable response times. ### 3. Optimized data structures Redis isn't just "key-value", it uses compact, carefully designed structures: - **List**, **Hash**, **Set**, **Sorted Set**, **Bitmap**, **HyperLogLog**, **Stream**. Every operation on them is implemented as efficiently as possible, at **O(1)** or **O(log n)**. *The takeaway:* operations run almost instantly, regardless of data volume. ### 4. Minimal system calls Redis works directly with memory and network sockets, using non-blocking I/O (**epoll/kqueue**). That cuts down wait time at the operating-system level. *The takeaway:* more operations in the same amount of time. ### 5. Persistent connections and a lightweight protocol Redis uses its own text protocol, RESP, simple, with no extra network "noise". Connections are long-lived, so there's no cost from constantly opening/closing TCP connections. *The takeaway:* fast data exchange between client and server. ### 6. Working with data directly in memory, no serialization Redis doesn't convert data into complex formats (JSON, SQL queries, etc.). It reads and writes it **directly in memory**. *The takeaway:* no parsing, indexes, or query plans, just instant operations. **The bottom line:** Redis is this fast because: - everything is stored in **RAM**, - it uses a **single-threaded, non-blocking architecture**, - it applies **optimized data structures** and a **simple protocol**. As a result, Redis can handle **hundreds of thousands of operations per second** with latency under **a millisecond**.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.