A cache stampede occurs when concurrent misses cause redundant work against the same dependency. Synchronized expiration is one trigger, but eviction, a cold deployment, or cache unavailability can create the same burst. A single popular key can be enough. The useful question is how many rebuilds reach the source while one result is still being computed. ...
Anycast gives an address several homes. Multiple sites announce the same prefix, and each network selects one usable path according to its BGP policy. A client usually lands at a topologically close replica without first contacting a global load balancer. When one site withdraws its announcement, the control plane can converge on another home. ...
A circuit breaker decides whether a new call should reach a dependency that appears unhealthy. It can reject promptly instead of spending resources on another likely failure. It does not repair that dependency, cancel calls already running, or prove that rejected work would have failed. Its value depends on the failure signals and recovery policy it actually implements. ...
A stale response can preserve access to a public manual during an origin outage. It can also preserve an obsolete price, revoked permission, or misleading status. Availability is not automatically more important than correctness. Choose the information that may remain usable, the conditions that permit reuse, and the maximum tolerable age before enabling this behavior. ...