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LLDsystem_design~12 mins

Multiple elevator coordination in LLD - Architecture Diagram

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System Overview - Multiple elevator coordination

This system manages multiple elevators in a building to efficiently handle passenger requests. It assigns elevators to floors based on current elevator positions, directions, and requests to minimize wait and travel times.

Architecture Diagram
User Requests
     |
     v
+-----------------+
|  Elevator System |
| +-------------+ |
| | Request     | |
| | Dispatcher  | |
| +-------------+ |
|       |         |
|       v         |
| +-------------+ |
| | Elevator 1  | |
| +-------------+ |
|       |         |
|       v         |
| +-------------+ |
| | Elevator 2  | |
| +-------------+ |
|       |         |
|       v         |
| +-------------+ |
| | Elevator N  | |
| +-------------+ |
+-----------------+
       |
       v
+-----------------+
|   Sensors &      |
|   Floor Status   |
+-----------------+
Components
User Requests
external_input
Passengers press elevator call buttons to request service.
Elevator System
system_controller
Central system coordinating elevator assignments and movements.
Request Dispatcher
service
Receives requests and assigns the best elevator based on current state.
Elevator 1
service
Individual elevator handling assigned requests and moving between floors.
Elevator 2
service
Another elevator instance handling requests.
Elevator N
service
Represents any additional elevators in the system.
Sensors & Floor Status
monitoring
Provides real-time elevator positions and door status to the system.
Request Flow - 5 Hops
User Requests → Request Dispatcher
Request Dispatcher → Sensors & Floor Status
Request Dispatcher → Elevator N (selected elevator)
Elevator N → Sensors & Floor Status
Elevator N → User Requests
Failure Scenario
Component Fails:Request Dispatcher
Impact:New elevator requests cannot be assigned, causing delays and possible system halt.
Mitigation:Use redundant dispatcher instances with failover and heartbeat monitoring to maintain availability.
Architecture Quiz - 3 Questions
Test your understanding
Which component decides which elevator should respond to a user request?
ARequest Dispatcher
BSensors & Floor Status
CElevator 1
DUser Requests
Design Principle
This design centralizes request handling to optimize elevator assignments using real-time position data, improving efficiency and passenger wait times while enabling scalability and fault tolerance through component separation.