This is meant to be a canonical Q&A for all the caching questions we get on meta
- What is caching?
- Where is caching employed across the network?
- Approximately how long ought it take for each cache to update?
asked May 1 '13 at 7:46
-
6"What is caching?" Have you bothered researching at all? Plus, how is that on topic for MSO? – BoltClock's a Unicorn May 1 '13 at 7:47
-
3See also, meta.stackexchange.com/questions/69164/… – George Duckett May 1 '13 at 7:50
-
1@GeorgeDuckett: yeah, already linked to it in the answer – Manishearth May 1 '13 at 7:51
-
@Manishearth: Sorry, didn't spot that! – George Duckett May 1 '13 at 7:51
-
@Manishearth I'd say George's link is the canonical one. If you want to create a FAQ, editing that one into shape might be a better approach perhaps? – Bart May 1 '13 at 8:08
-
@Bart: hmm, I could try that. Bit busy now, feel free to move everything over yourself if you wish :) – Manishearth May 1 '13 at 8:09
-
Nice one, until this is completed I've added new entry to the glossary. :) – Shadow Wizard Wearing Mask May 1 '13 at 8:16
-
@Manishearth I was attempting to edit the other one....let's say I would end up doing more damage than good. I'll leave it as it is. :) – Bart May 1 '13 at 8:45
-
@Bart: More or less why I didn't incorporate it when I found that question and was still drafting this :) – Manishearth May 1 '13 at 8:48
-
1Caching information on caching... – ronalchn May 1 '13 at 9:40
What is caching?
Caching is the storing of dynamic data in static form for reasonable periods of time. This reduces the number of queries required to display a page. The Stack Exchange engine caches heavily in places, to minimize cross-site queries. It uses Redis to help facilitate this. There is more on how exactly SO caches here.
Where is caching employed, and approximately how long should it take for the cache to update?
- Number of questions in a tag, on the tags page
- Rep/badges in the reputation leagues
- Reputation on meta
- New questions and number of answers on a question on the main page
- Assignment of questions to tags
- Tags are cached for searches and a post may still show up in a tag search after the tag is edited out
- On a user's profile:
- Rep/Badges on other sites
- Score/count in a tag (Once a day, ~3am UTC)
- "Votes Cast" (5 minutes)
- Flair
- Reputation counts on SO Careers (~1 day)
- Rep/badges on chat profile (can be force-refreshed by a moderator)
- Moderator status on chat
-
Also chat profiles may not update instantly when a user gets enough rep to chat. – tombull89 May 1 '13 at 8:35
-
related: Which tools and technologies are used to build the Stack Exchange Network? – gnat Jul 7 '17 at 12:54
-
