'Long release cycles: The joint deployment meant that there was increased fear of unintended production outages as debugging and rollback can be difficult for a deployment of this size. This drove the approach of the “release train”. Every two weeks, a “snapshot” of all modules was taken, and promoted to be a “release candidate”. This release candidate then went through exhaustive testing which attempted to cover as large a surface area as possible. This testing stage took about two weeks. Thus, depending on when the code change was merged, it could take anywhere between two and four weeks to reach production.'

I guess I'm just old, but I prefer the delay with a couple of weeks of testing versus pushing to prod and having the customer test the code.