Steady State

The term steady state is used to describe systems that are built in a way that makes possible their continuous operation. For instance, this would mean that a system should not store increasing amounts of data. Otherwise the system will have used up its entire capacity at some point and break down. Log files, for example, have to be deleted at some point. Usually they are only interesting during a certain time interval anyway. Another example is caching: when a cache keeps growing, it will at some point fill all available storage space. Therefore, values in the cache have to be flushed at some point to keep the cache size from continuously increasing.

Fail Fast

Timeouts are necessary only because another system may need a long time to respond. The idea behind Fail Fast is to address the problem from the other side: Each system should recognize errors as quickly as possible and indicate them immediately. When a call requires a certain service and that service is unavailable at the moment, the call can be directly answered with an error message. The same is true when other resources are not available at the time. Also, a call should be validated right at the start. When it contains errors, there is nothing to be gained by processing it and an error message can be returned immediately. The benefits of Fail Fast are identical to those offered by timeouts: A rapid failure uses up less resources and therefore results in a more stable system.

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