Suggest an editImprove this articleRefine the answer for “Why is Redis called an in-memory database?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)Redis is called an in-memory database because all data is stored and processed in RAM, rather than on a hard drive or SSD like traditional databases: RAM access is nanoseconds, while disk access is milliseconds. **Key point:** although Redis is in-memory, it can save a copy of the data to disk through RDB (periodic memory snapshots) or AOF (a log of every operation), so nothing is lost on restart.Shown above the full answer for quick recall.Answer (EN)ImageRedis is called an **in-memory database**, because **all data is stored and processed in RAM**, rather than on a hard drive or SSD like traditional databases. ### What this means technically - When an application writes or reads data from Redis, it's reaching into **RAM**, not the filesystem. - That makes operations **thousands of times faster**, since accessing RAM takes **nanoseconds**, while accessing disk takes **milliseconds**. ### How Redis persists data Although Redis is *in-memory*, it can **save a copy of the data to disk**, so nothing is lost on restart: - **RDB (snapshotting)**, periodic memory snapshots. - **AOF (Append Only File)**, logging every operation. On startup, Redis can restore data from these files back into memory. ### Why this matters - **Speed:** ideal for caches, sessions, queues. - **Low latency:** every operation runs instantly. - **Flexibility:** you can choose whether to persist data to disk, or keep everything only in memory (volatile). **Summary:** Redis is *in-memory* because **its primary storage is RAM**, and disk is used only for backup persistence. That's what gives Redis its **maximum data-access speed**.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.