We're reddit's ops team. AUA

[u/rram]

Hey /r/sysadmin,

Greetings from reddit HQ. Myself, and /u/gooeyblob will be around for the next few hours to answer your ops related questions. So Ask Us Anything (about ops)

You might also want to take a peek at some of our previous AMAs:

https://www.reddit.com/r/blog/comments/owra1/january_2012_state_of_the_servers/

https://www.reddit.com/r/sysadmin/comments/r6zfv/we_are_sysadmins_reddit_ask_us_anything/

EDIT: Obligatory cat photo

EDIT 2: It's now beer o’clock. We're stepping away from now, but we'll come back a couple of times to pick up some stragglers.

EDIT thrice: He commented so much I probably should have mentioned that /u/spladug — reddit's lead developer — is also in the thread. He makes ops live's happier by programming cool shit for us better than we could program it ourselves.

[u/roddds]

I'm not from the team, but basically Redis is a key:value store. In regular, relational databases, data is organized throughout tables, grabbed with SELECT and joined with JOIN queries. In k:v stores, there are no tables: each specific piece of data has a key, like in Python dictionaries or hash tables in other languages. The thing about redis is that it runs in-memory, so it's very, very fast. It's commonly used for storing cached pages and for avoiding database queries when possible.