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LLDsystem_design~12 mins

State diagrams in LLD - Architecture Diagram

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System Overview - State diagrams

A state diagram shows how a system or object changes its state in response to events. It helps us understand the different states and transitions clearly, like how a traffic light changes from green to yellow to red.

Key requirements include representing states, events that cause changes, and actions during transitions.

Architecture Diagram
  +------------+        event1        +------------+
  |  State A   | --------------------> |  State B   |
  +------------+                       +------------+
        ^                                    |
        |                                    | event2
        |                                    v
  +------------+ <-------------------- +------------+
  |  State C   |        event3           |  State D   |
  +------------+                       +------------+
Components
State A
state
Represents the initial or one of the possible states of the system.
State B
state
Represents a subsequent state after event1 occurs.
State C
state
Represents another state the system can be in, reachable from State D.
State D
state
Represents a state that transitions back to State C on event3.
event1
event
Triggers transition from State A to State B.
event2
event
Triggers transition from State B to State D.
event3
event
Triggers transition from State D to State C.
Request Flow - 3 Hops
State A → State B
State B → State D
State D → State C
Failure Scenario
Component Fails:Event signal delivery
Impact:If event signals are lost or delayed, the system may remain stuck in a state or transition incorrectly.
Mitigation:Use reliable event handling mechanisms and retries to ensure events trigger state changes correctly.
Architecture Quiz - 3 Questions
Test your understanding
Which component triggers the transition from State A to State B?
Aevent1
Bevent2
CState C
DState D
Design Principle
State diagrams clearly model how a system moves between different conditions based on events. This helps design predictable and manageable system behavior by visualizing states and transitions.