Mike Perham, Creator of Sidekiq: From Employment to Independence · Code Code Ship

I learned Ruby just in time to see Sidekiq take off. In the early 2010s, Ruby had seen a plethora of background job processors, from BackgroundJob to DelayedJob, Resque, and some others. Each improved and innovated in its own way on its predecessors. DelayedJob could run multiple jobs from a single Ruby instance (where BackgroundJob required loading the entire VM for each new job). Resque, in turn, improved upon this formula by storing jobs in Redis, which turned out to be much faster.