Coexistence
Coexistence is the degree to which a software product can operate efficiently while sharing its environment and resources with other independent systems.
“The degree to which a component or system can perform its required functions while sharing an environment and resources with other components or systems without a negative impact on any of them.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Coexistence?
Coexistence focuses on ensuring multiple applications can function together without negatively affecting each other's performance or operation.
Shared resources: Applications may share CPU, memory, storage, or networks.
Compatibility: Systems should operate together without unnecessary interference.
Testing focus: Verify stable operation alongside other applications.
Real World Example
A regulated product team is preparing a release where Coexistence appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Coexistence as interchangeable with nearby ISTQB terms. That makes test scope blurry and can lead to weak evidence for the release decision.
The tester anchors the discussion in the official definition, asks where the concept appears in the product, and designs examples that show the difference between Coexistence and similar ideas.
The page becomes useful in practice because Coexistence is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which test MOST directly evaluates coexistence?
Question 2
Which issue MOST indicates poor coexistence?
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