Background. Reliability in event-driven processes is difficult to judge when the conditions that make a process outcome acceptable are left implicit. Event handling may preserve, delay, replay, duplicate, or omit work, but the significance of these behaviours depends on what the process must protect. Replaying retained work may no longer protect correctness after the relevant deadline. A missed update may no longer matter. Deferred settlement may reduce duplicate harm while moving burden into reconciliation.

Objectives. This thesis develops a boundary-first framework for reasoning about reliability in event-driven processes. The aim is to make explicit what a process must protect before judging which process-handling model is appropriate.

Methods. The thesis follows a design science research approach. It develops the framework and examines it through a controlled, containerised empirical suite using transient and retained event handling. The suite compares deadline-constrained, state-oriented, and required-effect scenarios across three process-handling models: transient/immediate, retained/immediate, and retained/deferred. Each scenario combines a protected condition, a handling model, and a defined disturbance, allowing selected differences in preservation, replay, recovery, and settlement to be observed.The empirical comparison is exploratory and focuses on process-handling behaviou runder disturbance.

Results. The comparison shows that the value of replay, retention, immediate handling, and deferred settlement depends on the protected condition at stake. For deadline-constrained work, recovery matters only while unsettled work can still be resolved before expiry. For state-oriented work, replay matters when missed state remains relevant, while later state may overtake earlier misses. For required-effect work, replay can recover downstream handling gaps after emission, but not source omission. Deferred settlement can reduce immediate duplicate pressure by moving part of the burden into later reconciliation.

Conclusions. The thesis contributes a process-level framework for comparing handling choices under explicit correctness requirements. Its value lies in making the comparison inspectable: what the process must protect, what can threaten that requirement, which handling model is chosen, and what trade-off follows. The guide gives this reasoning a more concrete form, so that the design judgments behind handling choices can be understood more clearly.