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HLDsystem_design~12 mins

Leader election in HLD - Architecture Diagram

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System Overview - Leader election

This system ensures that among multiple distributed nodes, one node is chosen as the leader to coordinate tasks. The leader election process must be reliable, fault-tolerant, and ensure only one leader exists at any time.

Architecture Diagram
          +------------+          
          |   Clients  |          
          +-----+------+          
                |                 
                v                 
        +---------------+         
        | Load Balancer |         
        +-------+-------+         
                |                 
   +------------+------------+    
   |            |            |    
+--v--+     +---v---+    +---v---+
|Node1|     | Node2 |    | Node3 |
+--+--+     +---+---+    +---+---+
   |            |            |    
   +------------+------------+    
                |                 
          +-----v-----+           
          | Coordination|          
          |  Service   |          
          +-----+-----+           
                |                 
          +-----v-----+           
          |  Shared   |           
          |  Storage  |           
          +-----------+
Components
Clients
user
Users or external systems sending requests to the distributed nodes
Load Balancer
load_balancer
Distributes incoming client requests evenly among the nodes
Node1
service
Distributed node participating in leader election
Node2
service
Distributed node participating in leader election
Node3
service
Distributed node participating in leader election
Coordination Service
coordination_service
Manages leader election process and maintains leader state
Shared Storage
database
Stores leader information and election metadata reliably
Request Flow - 7 Hops
Clients → Load Balancer
Load Balancer → Node1
Node1 → Coordination Service
Coordination Service → Shared Storage
Shared Storage → Coordination Service
Coordination Service → Node1
Node1 → Clients
Failure Scenario
Component Fails:Coordination Service
Impact:Leader election cannot proceed, nodes cannot determine leader, system coordination halts
Mitigation:Use replicated coordination service instances with leader election among them to ensure high availability
Architecture Quiz - 3 Questions
Test your understanding
Which component ensures only one node acts as leader at a time?
AClients
BCoordination Service
CLoad Balancer
DShared Storage
Design Principle
This architecture uses a coordination service with shared storage to reliably elect a single leader among distributed nodes, ensuring fault tolerance and consistency in leader selection.