Backpressure connects a consumer’s limited capacity to the behavior of its producers. A full channel may make a producer wait, reject new work, or apply a deliberately chosen shedding policy. The important property is that the limit changes what upstream components do. A growing queue or a dashboard showing lag is evidence of imbalance, but neither is automatically a mechanism that controls admission. ...
When memory is exhausted, someone has to give. The kernel picks a victim by a policy you can read and influence, turning a crash into an order you can reason about. Exhaustion forces a choice Physical memory runs out, the allocator’s reclaim path has already been walked, and the kernel still cannot satisfy a grant — that is when the out-of-memory killer acts. It is not random; it computes which process to kill using a numeric score and terminates the least valuable candidate under pressure. The score weighs resident memory against a process’s share of the host, so a big, idle service that contributes little can be picked off while a small but essential one is spared. Understanding that the OOM killer runs on a score, not on who arrived first, is the whole basis for predicting its next move. ...
Clock synchronization reduces disagreement between machines’ civil-time readings. It supports certificate validity checks, timestamp interpretation, and many expiration policies, but it does not establish a perfect global clock. A host can emit well-formatted UTC while measuring the wrong instant. Applications still need to distinguish elapsed durations, absolute deadlines, and causal ordering rather than making them all depend on raw wall-clock comparisons. ...