How does the pipeline pattern work in concurrent systems?

In a pipeline, successive processing stages are connected by BlockingQueues, with each stage reading its input from one queue, doing its processing, and writing its output to the next queue in the chain. Every stage runs on its own thread or set of threads and executes concurrently with the others, so while stage two is processing item five, stage one can already be working on item six. The number of threads dedicated to each stage should be scaled roughly in proportion to how long that stage takes, so that slower stages get more threads to keep overall throughput balanced. Backpressure happens automatically without any extra code: if a downstream stage's output queue becomes full, its put() call simply blocks, which naturally slows down the upstream stages feeding it. Because of this, the pipeline's total throughput is always limited by its single slowest stage, and monitoring the depth of each intermediate queue is an effective way to identify exactly which stage is the bottleneck.