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LLDsystem_design~12 mins

Special moves (castling, en passant) in LLD - Architecture Diagram

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System Overview - Special moves (castling, en passant)

This system manages the special chess moves: castling and en passant. It ensures these moves follow chess rules and updates the game state accordingly.

Key requirements include validating move conditions, updating board state, and notifying players of move results.

Architecture Diagram
User
  |
  v
Move Validator Service
  |
  v
Game State Manager
  |      |
  v      v
Castling Handler  En Passant Handler
  |                |
  v                v
Board State Database
  |
  v
Notification Service
Components
User
user
Player who initiates moves
Move Validator Service
service
Checks if moves are legal including special moves
Game State Manager
service
Maintains current game state and coordinates special move handlers
Castling Handler
service
Validates and executes castling moves
En Passant Handler
service
Validates and executes en passant moves
Board State Database
database
Stores current positions of pieces and move history
Notification Service
service
Sends move results and updates to players
Request Flow - 9 Hops
User → Move Validator Service
Move Validator Service → Game State Manager
Game State Manager → Castling Handler
Game State Manager → En Passant Handler
Castling Handler → Game State Manager
En Passant Handler → Game State Manager
Game State Manager → Board State Database
Game State Manager → Notification Service
Notification Service → User
Failure Scenario
Component Fails:Board State Database
Impact:Game state cannot be updated or retrieved, causing move validation and game progress to halt
Mitigation:Use database replication and caching to allow reads from replicas; queue writes for retry; notify users of temporary issues
Architecture Quiz - 3 Questions
Test your understanding
Which component first checks if a move is a special move like castling or en passant?
AGame State Manager
BMove Validator Service
CCastling Handler
DBoard State Database
Design Principle
This design separates concerns by using dedicated handlers for special moves, ensuring clear validation and execution logic. It uses a central Game State Manager to coordinate and maintain consistency, while the database stores authoritative game state. Notifications keep players informed, supporting a responsive user experience.