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LLDsystem_design~12 mins

Activity diagrams in LLD - Architecture Diagram

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System Overview - Activity diagrams

An activity diagram visually shows the flow of actions or steps in a process or system. It helps understand how tasks move from one step to another, including decisions and parallel actions.

Key requirements include clear representation of activities, decisions, and flow direction to model workflows effectively.

Architecture Diagram
  +-----------------+       +-----------------+       +-----------------+
  |   Start Node    | ----> |   Activity 1    | ----> | Decision Node   |
  +-----------------+       +-----------------+       +-----------------+
                                                        /               \
                                                       /                 \
                                              +-----------------+   +-----------------+
                                              | Activity 2 (Yes) |   | Activity 3 (No)  |
                                              +-----------------+   +-----------------+
                                                       \                 /
                                                        \               /
                                                      +-----------------+
                                                      |   End Node      |
                                                      +-----------------+
Components
Start Node
start_node
Marks the beginning of the activity flow
Activity 1
activity
Represents the first action or step in the process
Decision Node
decision_node
Represents a branching point based on a condition
Activity 2 (Yes)
activity
Action taken if decision condition is true
Activity 3 (No)
activity
Action taken if decision condition is false
End Node
end_node
Marks the end of the activity flow
Request Flow - 6 Hops
Start Node → Activity 1
Activity 1 → Decision Node
Decision Node → Activity 2 (Yes)
Decision Node → Activity 3 (No)
Activity 2 (Yes) → End Node
Activity 3 (No) → End Node
Failure Scenario
Component Fails:Decision Node
Impact:The process cannot branch correctly, causing the flow to stop or take wrong paths.
Mitigation:Add validation checks before the decision node and fallback default paths to ensure process continuity.
Architecture Quiz - 3 Questions
Test your understanding
What is the purpose of the Decision Node in an activity diagram?
ATo represent a branching point based on a condition
BTo start the process
CTo end the process
DTo perform an action
Design Principle
Activity diagrams use clear nodes and flows to model processes visually, helping teams understand and communicate workflows with decisions and parallel steps.