Backpressure
In plain terms
A mechanism to slow producers when consumers can't keep up.
Going deeper
Backpressure signals upstream to reduce its rate when downstream is overwhelmed, preventing overload and data loss. It balances flow in pipelines.
Under the hood
Reactive streams implement it; without it, fast producers crash slow consumers or exhaust buffers.
Examples
Reactive streams, message queues, flow control, streaming systems, RxJS.
Think of it like...
Like a checkout clerk waving the line to slow down when they're swamped.