Back Pressure Conflicting Definitions

[aurainsignia]

If queues start to grow significantly, the queue size can become larger than memory, resulting in cache misses, disk reads, and even slower performance. Back pressure can help by limiting the queue size, thereby maintaining a high throughput rate and good response times for jobs already in the queue.

I'm finding conflicting definitions of what back pressure is. The wording here seems to suggest that back pressure is the solution of limiting queue size to prevent performance degradation when input grows too large on unbound queues. When checking other sources though, back pressure seems to be described as the problem of the input growing too large for the queue to handle, rather than the solution to the input growing too large. From that definition, the sentence "Back pressure can help by limiting the queue size ..." doesn't make any sense. Is back pressure the problem, or the solution?

Sources defining back pressure as the problem:

• https://akashrajpurohit.com/blog/understanding-back-pressure-in-message-queues-a-guide-for-developers/
• https://medium.com/@jayphelps/backpressure-explained-the-flow-of-data-through-software-2350b3e77ce7
• https://softwareengineering.stackexchange.com/questions/430396/how-to-handle-backpressure-in-message-queue