Klarna is currently undergoing a migration where its purchase taking capability is being ported from its very large, monolithic Erlang system that performs many varied business tasks to a specialized one for taking purchases using current Erlang best practices such as rebar and other standard open source offerings (lager, folsom, riak, rabbit, and more) deployed with Chef. Focal points will be how Klarna's regular weekly release cycle has allowed this to be an incremental process, as well as how we regression test a distributed system with heterogenous components.