Suggest an edit

Improve this article

Refine the answer for “What is Redis?”. Your changes go to moderation before they’re published.

Approval required

Content

What you’re changing

Title (EN)

Short answer (EN)

Shown above the full answer for quick recall.

Answer (EN)

**Redis** is an **in-memory database** used for **very fast data storage and access**.

Its name stands for **REmote DIctionary Server**.

### The main idea

Redis stores data **in RAM**, not on disk, so it runs **tens of times faster** than ordinary databases (e.g. PostgreSQL or MySQL).

### Data types

Redis isn't just "key-value". It supports several structures:

- **strings**, plain values;
- **lists**, ordered collections;
- **sets**, unique elements;
- **hashes**, fields and values (like a dictionary);
- **sorted sets**, with priorities (rankings, leaderboards);
- **streams, bitmaps, geospatial data**, and more.

### How it works

- All data is stored **in RAM**,
but Redis can **periodically save** it to disk (a snapshot) or to a log (AOF), so nothing is lost on a failure.
- Access follows the **key → value** principle.

### Main uses

- **Caching** (speeding up web services).
- **Storing user sessions**.
- **Message queues** and **pub/sub systems**.
- **Counters, rankings, timers** (thanks to atomic operations).

### Characteristics

- Very high speed (operations take milliseconds).
- Supports **TTL**, a key's time to live (it's removed automatically).
- Can run as a **cluster** for scaling.

**Summary:**
Redis is an **extremely fast in-memory database**, a great fit for **caches, queues, and real-time systems**, where access speed matters more than complex relationships.

Markdown · drag & drop images · ⌘B / ⌘I shortcuts212 words

For the reviewer

Note to the moderator (optional)

Visible only to the moderator. Helps review go faster.