Editing Memcached (section)

{{Short description|Open source distributed memory caching system}}
{{Infobox software
| name = Memcached
| logo = Memcached.svg
| logo size = 100px
| screenshot = 
| caption = 
| developer = Dormando
| released = {{start date|2003|5|22}}
| latest release version = {{wikidata|property|edit|reference|P348}}
| latest release date = {{start date and age|{{wikidata|qualifier|P348|P577}}}}
| operating system = [[Cross-platform]]
| programming language = [[C (programming language)|C]]
| genre = distributed memory caching system
| license = [[Revised BSD license]]<ref name="Memcached license">{{cite web | url=https://github.com/memcached/memcached/blob/master/COPYING | title=Memcached license | publisher=[[GitHub]] | access-date=2014-06-27}}</ref>
}}
'''Memcached''' (pronounced variously /mɛmkæʃˈdiː/ ''mem-cash-dee'' or /ˈmɛmkæʃt/ ''mem-cashed'') is a general-purpose distributed [[memory caching|memory-caching]] system. It is often used to speed up dynamic [[database]]-driven websites by caching data and [[Object (computer science)|objects]] in [[Random-access memory|RAM]] to reduce the number of times an external data source (such as a database or API) must be read. Memcached is [[free and open-source software]], licensed under the [[Revised BSD license]].<ref name="Memcached license" /> Memcached runs on [[Unix-like]] operating systems ([[Linux]] and [[macOS]]) and on [[Microsoft Windows]]. It depends on the [[libevent]] library.

Memcached's [[Application Programming Interface|API]]s provide a very large [[hash table]] distributed across multiple machines. When the table is full, subsequent inserts cause older data to be purged in [[least recently used]] (LRU) order.<ref>{{cite web|url=http://code.google.com/p/memcached/wiki/NewOverview |title=Google Code Archive - Long-term storage for Google Code Project Hosting |website=Code.google.com |access-date=2017-06-25}}</ref><ref>{{cite web|url=http://code.google.com/p/memcached/wiki/NewUserInternals |title=Google Code Archive - Long-term storage for Google Code Project Hosting |website=Code.google.com |access-date=2017-06-25}}</ref> Applications using Memcached typically layer requests and additions into RAM before falling back on a slower backing store, such as a database.

Memcached has no internal mechanism to track misses which may happen. However, some third party utilities provide this functionality.

Memcached was first developed by [[Brad Fitzpatrick]] for his website [[LiveJournal]], on May 22, 2003.<ref>[http://community.livejournal.com/changelog/637455.html]. Community.livejournal.com (2003-05-22). Retrieved on 2013-09-18.</ref><ref>[http://community.livejournal.com/lj_dev/539656.html]. Community.livejournal.com (2003-05-27). Retrieved on 2013-09-18.</ref> It was originally written in [[Perl]], then later rewritten in [[C (programming language)|C]] by Anatoly Vorobey, then employed by LiveJournal.<ref>{{cite web|url=http://lj-dev.livejournal.com/539656.html |archive-url=https://web.archive.org/web/20130225020652/http://lj-dev.livejournal.com/539656.html |url-status=dead |archive-date=2013-02-25 |title=lj_dev: memcached |date=2013-02-25 |access-date=2017-06-25}}</ref> Memcached is now used by many other systems, including [[YouTube]],<ref>{{cite video|people=Cuong Do Cuong (Engineering manager at YouTube/Google)|title=Seattle Conference on Scalability: YouTube Scalability|url=http://video.google.com/videoplay?docid=-6304964351441328559|medium=Online Video - 26th minute|publisher=Google Tech Talks|location=Seattle|date=June 23, 2007}}</ref> [[Reddit]],<ref>{{cite web|url=http://carsonified.com/blog/dev/steve-huffman-on-lessons-learned-at-reddit/|archive-url=https://web.archive.org/web/20100517063632/http://carsonified.com/blog/dev/steve-huffman-on-lessons-learned-at-reddit/|url-status=dead|archive-date=2010-05-17|title=Steve Huffman on Lessons Learned at Reddit &#124; Carsonified|last=Whitaker|first=Keir|date=2010-05-17|access-date=2017-06-25}}</ref> [[Facebook]],<ref>{{cite web|url=http://www.facebook.com/note.php?note_id=39391378919&ref=mf|title=Scaling memcached at Facebook|date=2008-12-12|website=Facebook.com|access-date=2017-06-25}}</ref><ref>{{cite book|url=https://www.usenix.org/conference/nsdi13/scaling-memcache-facebook|title=Scaling Memcache at Facebook|year=2002 |publisher=USENIX|isbn=9781931971003 |access-date=2017-06-25}}</ref> [[Pinterest]],<ref>{{cite news|url=https://engineering.pinterest.com/blog/building-pinterest-cloud|title=Building Pinterest in the cloud|date=2013-06-19|newspaper=Pinterest Careers|access-date=2018-03-09}}</ref><ref>{{cite web|url=https://github.com/pinterest/pymemcache|title= A comprehensive, fast, pure-Python memcached client|date=2018-01-08|website=Github.com|access-date=2018-03-09}}</ref> [[Twitter]],<ref>{{cite web|url=http://blog.twitter.com/2008/05/its-not-rocket-science-but-its-our-work.html|title=It's Not Rocket Science, But It's Our Work|date=2008-06-01|website=Blog.twitter.com|access-date=2017-06-25}}</ref> [[Wikipedia]],<ref>{{cite web|url=https://www.mediawiki.org/wiki/Memcached|title=memcached|publisher=MediaWiki|access-date=2017-06-25}}</ref> and [[Method Studios]].<ref>{{Citation|title=Rez BoF, SIGGRAPH 2019|url=https://www.youtube.com/watch?v=y5VSPeeqJbM |archive-url=https://ghostarchive.org/varchive/youtube/20211212/y5VSPeeqJbM| archive-date=2021-12-12 |url-status=live|language=en|access-date=2019-08-09}}{{cbignore}}</ref> [[Google App Engine]], [[Google Cloud Platform]], [[Microsoft Azure]], [[IBM Bluemix]] and [[Amazon Web Services]] also offer a Memcached service through an API.<ref>{{cite web|url=http://code.google.com/appengine/docs/python/memcache/usingmemcache.html|title=Memcache Examples &#124; App Engine standard environment for Python &#124; Google Cloud Platform|date=2017-03-22|website=Code.google.com|access-date=2017-06-25}}</ref><ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/windowsazure/hh914161.aspx|title=About In-Role Cache for Azure Cache|date=2015-08-25|website=Msdn.microsoft.com|access-date=2017-06-25}}</ref><ref>{{cite web|url=http://www.datacenterknowledge.com/archives/2014/09/23/redis-labs-3000-paying-cloud-memory-nosql-customers/|title=Redis Labs: We Have 3,000 Paying Cloud In-Memory NoSQL Customers|last=Verge|first=Jason|date=2014-09-23|access-date=2016-09-10|work=Data Center Knowledge}}</ref><ref>{{cite web|url=http://aws.amazon.com/elasticache/|title=AWS &#124; Amazon ElastiCache – in-memory data store and cache|website=Aws.amazon.com|access-date=2017-06-25}}</ref>