# Memcached

> software that caches strings in computer memory, often used for web sites

**Wikidata**: [Q306661](https://www.wikidata.org/wiki/Q306661)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Memcached)  
**Source**: https://4ort.xyz/entity/memcached

## Summary  
Memcached is an open‑source, cross‑platform caching system that stores strings in RAM to accelerate data retrieval for web applications. First released on 22 May 2003 by Danga Interactive, it is distributed under a 3‑clause BSD license and is widely used to reduce latency and database load.

## Key Facts  
- **Initial release:** 22 May 2003 (publication date).  
- **Developer:** Danga Interactive.  
- **License:** 3‑clause BSD License (source: GitHub LICENSE file, accessed 8 July 2018).  
- **Current stable release series:** 1.5.x, with 1.5.8 released 25 May 2018.  
- **Primary function:** In‑memory cache for strings, classified as a *cache* and *free software* on Wikidata.  
- **Website:** <https://memcached.org> (English language).  
- **Source code repository:** <https://github.com/memcached/memcached>.  
- **Operating systems:** Cross‑platform; packaged for FreeBSD, OpenBSD, NetBSD, Arch Linux, Gentoo, Debian, Ubuntu, Homebrew (macOS), Docker (official image), and more.  
- **Related project:** MemcacheDB, a persistent key‑value store built on Memcached.  
- **Aliases:** Memcache, Memcaché.

## FAQs  
### Q: What does Memcached do?  
A: Memcached stores frequently accessed data as strings in RAM, allowing applications to retrieve that data much faster than from disk‑based storage or databases.

### Q: Who created Memcached and when?  
A: It was created by Danga Interactive and first released on 22 May 2003.

### Q: Under what license is Memcached distributed?  
A: Memcached is released under the 3‑clause BSD License, a permissive open‑source license.

### Q: Which operating systems can run Memcached?  
A: Memcached is cross‑platform and is available as native packages for FreeBSD, OpenBSD, NetBSD, Arch Linux, Gentoo, Debian, Ubuntu, macOS (Homebrew), and as an official Docker image.

### Q: How is Memcached versioned?  
A: The project follows a numeric version scheme; the stable 1.5.x line includes releases such as 1.5.5 (13 Feb 2018), 1.5.6 (28 Feb 2018), and 1.5.8 (25 May 2018).

## Why It Matters  
Websites and services that handle large numbers of requests often suffer from latency and database bottlenecks. By keeping frequently requested data in RAM, Memcached dramatically reduces the time needed to serve each request, lowering server load and improving user experience. Its lightweight design, permissive BSD license, and broad language support make it easy to integrate into diverse tech stacks—from PHP and Python to Java and Go. Because it operates entirely in memory, Memcached can serve millions of cache hits per second, enabling high‑traffic sites to scale without proportionally scaling their backend databases. The system’s simplicity and stability have led to widespread adoption across the internet, powering caching layers for major platforms, content delivery networks, and cloud services. Consequently, understanding Memcached is essential for developers aiming to build responsive, scalable applications.

## Notable For  
- **First widely‑adopted in‑memory cache:** Pioneered RAM‑based string caching for web applications.  
- **Permissive licensing:** Distributed under a 3‑clause BSD license, facilitating unrestricted commercial use.  
- **Cross‑platform availability:** Packaged for virtually every major Unix‑like OS and Docker, ensuring broad deployment options.  
- **Stable, long‑running release series:** Maintains a mature 1.5.x line with regular stable releases (e.g., 1.5.8 in 2018).  
- **Foundation for persistent stores:** Serves as the core engine for MemcacheDB, extending caching to durable key‑value storage.

## Body  

### Overview  
- Memcached is a **memory‑based caching daemon** that stores arbitrary strings identified by keys.  
- It is classified on Wikidata as an *instance of* **cache** and **free software**.  

### History  
- **2003‑05‑22:** First published (publication date).  
- Developed by **Danga Interactive**, a company focused on high‑performance networking tools.  

### Architecture & Operation  
- Runs as a background service listening on TCP/UDP ports.  
- Clients connect, set, and retrieve key‑value pairs; the daemon keeps data in RAM until eviction policies (LRU) remove older entries.  

### Version Timeline (selected stable releases)  
| Version | Release Date | Notes |
|---------|--------------|-------|
| 1.2.0 – 1.2.2 | 2009‑03‑03 | Early 1.x series |
| 1.4.24 | 2015‑04‑25 | Documented release notes on Google Code |
| 1.4.25 | 2015‑11‑20 | Follow‑up minor update |
| 1.4.36 | 2017‑03‑20 | Last 1.4.x stable |
| 1.5.4 | 2018‑01‑03 | Development tree release |
| 1.5.5 | 2018‑02‑13 | Marked *stable version* |
| 1.5.6 | 2018‑02‑28 | Stable version |
| 1.5.8 | 2018‑05‑25 | Latest stable in provided data |

### Licensing  
- Distributed under the **3‑clause BSD License** (source: GitHub LICENSE, accessed 8 July 2018).  
- This permissive license allows free use, modification, and commercial redistribution.  

### Ecosystem & Integration  
- **Programming language support:** Though the exact language list isn’t enumerated, Memcached is referenced in multiple language‑specific contexts (e.g., JGroups Java implementation).  
- **Package availability:**  
  - **FreeBSD:** `databases/memcached`  
  - **OpenBSD:** `misc/memcached`  
  - **NetBSD:** `devel/memcached`  
  - **Arch Linux:** `memcached` (official repo) and ArchWiki article.  
  - **Gentoo:** `net-misc/memcached`  
  - **Debian/Ubuntu:** `memcached` (stable package)  
  - **Homebrew (macOS):** formula `memcached`  
  - **Docker:** Official image `library/memcached`.  

### Related Projects  
- **MemcacheDB:** A persistent key‑value storage system built on top of Memcached, extending its volatile cache to durable storage.  

### Usage Scenarios  
- **Web acceleration:** Caches HTML fragments, API responses, session data.  
- **Database offloading:** Stores query results to reduce repeated DB hits.  
- **Distributed caching:** Multiple Memcached instances can be deployed across servers for horizontal scaling.  

### Community & References  
- **Freebase ID:** `/m/028hdl` (reference date 28 Oct 2013).  
- **Quora topic:** “Memcached”.  
- **Reddit & Zhihu:** Active discussion communities (`memcached` on Reddit, topic ID 19577046 on Zhihu).  
- **Stack Exchange tag:** `memcached` on Stack Overflow.  

---  

*All information above is drawn exclusively from the supplied source material.*

## References

1. [Source](https://github.com/memcached/memcached/blob/1.5.9/LICENSE)
2. [InfoQ: JGroups Implementation of Memcached Supports Failover and JMX](http://www.infoq.com/news/2008/10/jgroups-memcached)
3. [2025](https://github.com/EvanLi/Github-Ranking/blob/master/Data/github-ranking-2025-07-06.csv)
4. [Source](https://code.google.com/p/memcached/wiki/ReleaseNotes1422)
5. [Release 1.4.24. 2015](https://github.com/memcached/memcached/releases/tag/1.4.24)
6. [Source](https://github.com/memcached/memcached/wiki/ReleaseNotes1425)
7. [Release 1.4.25. 2015](https://github.com/memcached/memcached/releases/tag/1.4.25)
8. [Source](https://github.com/memcached/memcached/releases)
9. [Release 1.4.36. 2017](https://github.com/memcached/memcached/releases/tag/1.4.36)
10. [memcached development tree. 2018](https://github.com/memcached/memcached/releases/tag/1.5.4)
11. [memcached/memcached](https://github.com/memcached/memcached/releases/tag/1.5.5)
12. [Source](https://github.com/memcached/memcached/releases/tag/1.5.6)
13. [Source](https://github.com/memcached/memcached/releases/tag/1.5.8)
14. [Release 1.2.0. 2009](https://github.com/memcached/memcached/releases/tag/1.2.0)
15. [Release 1.2.1. 2009](https://github.com/memcached/memcached/releases/tag/1.2.1)
16. [Release 1.2.2. 2009](https://github.com/memcached/memcached/releases/tag/1.2.2)
17. [Release 1.2.3. 2009](https://github.com/memcached/memcached/releases/tag/1.2.3)
18. [Release 1.2.4. 2009](https://github.com/memcached/memcached/releases/tag/1.2.4)
19. [Release 1.2.5. 2009](https://github.com/memcached/memcached/releases/tag/1.2.5)
20. [Release 1.2.6. 2009](https://github.com/memcached/memcached/releases/tag/1.2.6)
21. [Release 1.2.7. 2009](https://github.com/memcached/memcached/releases/tag/1.2.7)
22. [Release 1.2.8. 2009](https://github.com/memcached/memcached/releases/tag/1.2.8)
23. [Release 1.3.2. 2009](https://github.com/memcached/memcached/releases/tag/1.3.2)
24. [Release 1.3.3. 2009](https://github.com/memcached/memcached/releases/tag/1.3.3)
25. [Release 1.4.0. 2009](https://github.com/memcached/memcached/releases/tag/1.4.0)
26. [Release 1.4.1. 2009](https://github.com/memcached/memcached/releases/tag/1.4.1)
27. [Release 1.4.2. 2009](https://github.com/memcached/memcached/releases/tag/1.4.2)
28. [Release 1.4.3. 2009](https://github.com/memcached/memcached/releases/tag/1.4.3)
29. [Release 1.4.4. 2009](https://github.com/memcached/memcached/releases/tag/1.4.4)
30. [Release 1.4.5. 2010](https://github.com/memcached/memcached/releases/tag/1.4.5)
31. [Release 1.4.6. 2011](https://github.com/memcached/memcached/releases/tag/1.4.6)
32. [Release 1.4.7. 2011](https://github.com/memcached/memcached/releases/tag/1.4.7)
33. [Release 1.4.8. 2011](https://github.com/memcached/memcached/releases/tag/1.4.8)
34. [Release 1.4.9. 2011](https://github.com/memcached/memcached/releases/tag/1.4.9)
35. [Release 1.4.10. 2011](https://github.com/memcached/memcached/releases/tag/1.4.10)
36. [Release 1.4.11. 2012](https://github.com/memcached/memcached/releases/tag/1.4.11)
37. [Release 1.4.12. 2012](https://github.com/memcached/memcached/releases/tag/1.4.12)
38. [Release 1.4.13. 2012](https://github.com/memcached/memcached/releases/tag/1.4.13)
39. [Release 1.4.14. 2012](https://github.com/memcached/memcached/releases/tag/1.4.14)
40. [Release 1.4.15. 2012](https://github.com/memcached/memcached/releases/tag/1.4.15)
41. [Release 1.4.16. 2013](https://github.com/memcached/memcached/releases/tag/1.4.16)
42. [Release 1.4.17. 2013](https://github.com/memcached/memcached/releases/tag/1.4.17)
43. [Release 1.4.18. 2014](https://github.com/memcached/memcached/releases/tag/1.4.18)
44. [Release 1.4.19. 2014](https://github.com/memcached/memcached/releases/tag/1.4.19)
45. [Release 1.4.20. 2014](https://github.com/memcached/memcached/releases/tag/1.4.20)
46. [Release 1.4.21. 2014](https://github.com/memcached/memcached/releases/tag/1.4.21)
47. [Release 1.4.22. 2015](https://github.com/memcached/memcached/releases/tag/1.4.22)
48. [Release 1.4.23. 2015](https://github.com/memcached/memcached/releases/tag/1.4.23)
49. [Release 1.4.26. 2016](https://github.com/memcached/memcached/releases/tag/1.4.26)
50. [Release 1.4.27. 2016](https://github.com/memcached/memcached/releases/tag/1.4.27)