# Backpressure Status: Growing Backpressure is the ability of a system to slow down upstream work when downstream capacity is limited. ## Mental Model If a downstream service, queue, database, or worker pool is overloaded, the upstream caller needs a signal to stop sending unlimited work. Without backpressure, load keeps flowing into the system until queues grow, latency rises, memory fills, retries multiply, and the failure spreads. ## Why It Matters Backpressure turns overload from an uncontrolled collapse into an explicit flow-control problem. Examples: - A queue stops accepting new jobs. - A service returns `429` or `503`. - A TCP receiver advertises a smaller window. - A worker pool rejects work when all workers are saturated. ## Related - [[Topics/Production Engineering]] - [[Topics/Distributed Systems]] - [[Field Notes/Tail Latency]]